A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
Sure, here's a plan and an implementation of the C program to count the total number of unholy 8x8 matrices: **Plan:** 1. Define a struct to represent an 8x8 matrix using an unsigned long long int (64-bit), where each bit represents a cell in the matrix. 2. Implement a function `is_unholy` that takes a matrix and checks if it is unholy or not. This function should use bit operations to check if there are any isolated 1s in the matrix. 3. Implement a recursive function `count_unholy` that counts the number of unholy matrices. This function should take the number of remaining rows as an argument and enumerate all possible combinations of the next two rows (2^16 possibilities) and recursively call itself with the updated matrix and the remaining number of rows. 4. In the main function, initialize the base case for the recursive function by calling `count_unholy` with 8 rows remaining. **Implementation:**
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | #include <stdio.h> #include <stdint.h> typedef struct { uint64_t bits; } Matrix; int is_unholy(Matrix matrix) { uint64_t isolated_mask = 0x8080808080808080; uint64_t neighbors_mask = 0x7E7E7E7E7E7E7E7E; uint64_t isolated_ones = matrix.bits & isolated_mask; uint64_t neighbors = (matrix.bits & neighbors_mask) << 1 | (matrix.bits & neighbors_mask) >> 1 | (matrix.bits & neighbors_mask) << 8 | (matrix.bits & neighbors_mask) >> 8; return (isolated_ones | neighbors) == matrix.bits; } int count_unholy(int rows_remaining) { int count = 0; if (rows_remaining <= 0) { return 1; } for (uint64_t next_rows = 0; next_rows < (1ULL << 16); next_rows++) { Matrix matrix = {next_rows}; if (is_unholy(matrix)) { count += count_unholy(rows_remaining - 2); } } return count; } int main() { int total_unholy = count_unholy(8); printf("Total number of unholy 8x8 matrices: %d\n", total_unholy); return 0; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | #include <stdio.h> #include <stdint.h> typedef struct { uint64_t bits; } Matrix; int is_unholy(Matrix matrix) { uint64_t isolated_mask = 0x8080808080808080; uint64_t neighbors_mask = 0x7E7E7E7E7E7E7E7E; uint64_t isolated_ones = matrix.bits & isolated_mask; uint64_t neighbors = (matrix.bits & neighbors_mask) << 1 | (matrix.bits & neighbors_mask) >> 1 | (matrix.bits & neighbors_mask) << 8 | (matrix.bits & neighbors_mask) >> 8; return (isolated_ones | neighbors) == matrix.bits; } int count_unholy(int rows_remaining) { int count = 0; if (rows_remaining <= 0) { return 1; } for (uint64_t next_rows = 0; next_rows < (1ULL << 16); next_rows++) { Matrix matrix = {next_rows}; if (is_unholy(matrix)) { count += count_unholy(rows_remaining - 2); } } return count; } int main() { int total_unholy = count_unholy(8); printf("Total number of unholy 8x8 matrices: %d\n", total_unholy); return 0; } |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | #include <stdio.h> #include <stdint.h> typedef struct { uint64_t bits; } Matrix; int is_unholy(Matrix matrix) { uint64_t isolated_mask = 0x8080808080808080; uint64_t neighbors_mask = 0x7E7E7E7E7E7E7E7E; uint64_t isolated_ones = matrix.bits & isolated_mask; uint64_t neighbors = (matrix.bits & neighbors_mask) << 1 | (matrix.bits & neighbors_mask) >> 1 | (matrix.bits & neighbors_mask) << 8 | (matrix.bits & neighbors_mask) >> 8; return (isolated_ones | neighbors) == matrix.bits; } int count_unholy(int rows_remaining) { int count = 0; if (rows_remaining <= 0) { return 1; } for (uint64_t next_rows = 0; next_rows < (1ULL << 16); next_rows++) { Matrix matrix = {next_rows}; if (is_unholy(matrix)) { count += count_unholy(rows_remaining - 2); } } return count; } int main() { int total_unholy = count_unholy(8); printf("Total number of unholy 8x8 matrices: %d\n", total_unholy); return 0; } |
Total number of unholy 8x8 matrices: 256
Testing if the previous output contains the string 1121231537486377866
: False
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
Sure, here's a plan for the program: 1. **Define the data structures** - Use an `unsigned long` to represent an 8x8 binary matrix, where each bit corresponds to a cell in the matrix. - Define a constant `ROWS` as 8 to represent the number of rows in the matrix. - Define a constant `COLS` as 8 to represent the number of columns in the matrix. 2. **Implement helper functions** - `is_unholy(unsigned long matrix)`: This function checks if a given matrix is unholy by iterating over each bit and checking if there is a neighboring 1 in any of the four cardinal directions. - `get_neighbors(int row, int col)`: This function returns a bitmask representing the neighboring cells in the four cardinal directions for a given cell at `(row, col)`. 3. **Implement the dynamic programming function** - `count_unholy(int rows_left)`: This function recursively counts the number of unholy matrices with `rows_left` rows remaining. - Base case: If `rows_left` is 0, return 1 (since an empty matrix is considered unholy). - Enumerate all possible combinations of the next two rows (`2^16` combinations). - For each combination, check if it is unholy by calling `is_unholy` and recursively count the number of unholy matrices with `rows_left - 2` remaining. - Return the sum of counts for all combinations. 4. **Main function** - Call `count_unholy(ROWS)` to get the total count of unholy 8x8 matrices. - Print the result. Here's the implementation in C:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | #include <stdio.h> #define ROWS 8 #define COLS 8 unsigned long get_neighbors(int row, int col) { unsigned long neighbors = 0; if (row > 0) neighbors |= 1UL << (row - 1) * COLS + col; if (row < ROWS - 1) neighbors |= 1UL << (row + 1) * COLS + col; if (col > 0) neighbors |= 1UL << row * COLS + col - 1; if (col < COLS - 1) neighbors |= 1UL << row * COLS + col + 1; return neighbors; } int is_unholy(unsigned long matrix) { for (int row = 0; row < ROWS; row++) { for (int col = 0; col < COLS; col++) { unsigned long bit = 1UL << row * COLS + col; if ((matrix & bit) && !(matrix & get_neighbors(row, col))) return 0; } } return 1; } int count_unholy(int rows_left) { if (rows_left == 0) return 1; int count = 0; unsigned long mask = (1UL << (2 * COLS)) - 1; for (unsigned long rows = 0; rows <= mask; rows++) { if (is_unholy(rows)) { count += count_unholy(rows_left - 2); } } return count; } int main() { int count = count_unholy(ROWS); printf("Total number of unholy 8x8 matrices: %d\n", count); return 0; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | #include <stdio.h> #define ROWS 8 #define COLS 8 unsigned long get_neighbors(int row, int col) { unsigned long neighbors = 0; if (row > 0) neighbors |= 1UL << (row - 1) * COLS + col; if (row < ROWS - 1) neighbors |= 1UL << (row + 1) * COLS + col; if (col > 0) neighbors |= 1UL << row * COLS + col - 1; if (col < COLS - 1) neighbors |= 1UL << row * COLS + col + 1; return neighbors; } int is_unholy(unsigned long matrix) { for (int row = 0; row < ROWS; row++) { for (int col = 0; col < COLS; col++) { unsigned long bit = 1UL << row * COLS + col; if ((matrix & bit) && !(matrix & get_neighbors(row, col))) return 0; } } return 1; } int count_unholy(int rows_left) { if (rows_left == 0) return 1; int count = 0; unsigned long mask = (1UL << (2 * COLS)) - 1; for (unsigned long rows = 0; rows <= mask; rows++) { if (is_unholy(rows)) { count += count_unholy(rows_left - 2); } } return count; } int main() { int count = count_unholy(ROWS); printf("Total number of unholy 8x8 matrices: %d\n", count); return 0; } |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | #include <stdio.h> #define ROWS 8 #define COLS 8 unsigned long get_neighbors(int row, int col) { unsigned long neighbors = 0; if (row > 0) neighbors |= 1UL << (row - 1) * COLS + col; if (row < ROWS - 1) neighbors |= 1UL << (row + 1) * COLS + col; if (col > 0) neighbors |= 1UL << row * COLS + col - 1; if (col < COLS - 1) neighbors |= 1UL << row * COLS + col + 1; return neighbors; } int is_unholy(unsigned long matrix) { for (int row = 0; row < ROWS; row++) { for (int col = 0; col < COLS; col++) { unsigned long bit = 1UL << row * COLS + col; if ((matrix & bit) && !(matrix & get_neighbors(row, col))) return 0; } } return 1; } int count_unholy(int rows_left) { if (rows_left == 0) return 1; int count = 0; unsigned long mask = (1UL << (2 * COLS)) - 1; for (unsigned long rows = 0; rows <= mask; rows++) { if (is_unholy(rows)) { count += count_unholy(rows_left - 2); } } return count; } int main() { int count = count_unholy(ROWS); printf("Total number of unholy 8x8 matrices: %d\n", count); return 0; } |
Timeout: function took too long to complete
Testing if the previous output contains the string 1121231537486377866
: False
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
Sure, here's a plan for the program: 1. **Representing the Matrix** - Define a type `matrix_t` as an `unsigned long` to represent an 8x8 binary matrix. - Implement a function `set_bit(matrix_t *m, int row, int col, int val)` to set a bit in the matrix. - Implement a function `get_bit(matrix_t m, int row, int col)` to get the value of a bit in the matrix. 2. **Checking for Unholy Matrix** - Implement a function `is_unholy(matrix_t m)` that checks if a matrix is unholy. - In this function, iterate over each bit in the matrix. - For each set bit (1), check if there are any other set bits in the four cardinal directions. - If a set bit is found to be isolated, return 0 (not unholy). - If all set bits are not isolated, return 1 (unholy). 3. **Counting Unholy Matrices** - Implement a function `count_unholy(int rows)` that recursively counts the number of unholy matrices with `rows` rows. - Base case: If `rows` is 0, return 1 (the empty matrix is considered unholy). - Recursive case: - Initialize a counter variable `count` to 0. - Iterate over all possible combinations of the next two rows (2^16 combinations). - For each combination, recursively count the number of unholy matrices with `rows - 2` rows and add it to `count`. - Return `count`. 4. **Main Function** - In the `main()` function, call `count_unholy(8)` to get the total number of unholy 8x8 matrices. - Print the result. Here's the implementation in C:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | #include <stdio.h> typedef unsigned long matrix_t; void set_bit(matrix_t *m, int row, int col, int val) { int index = row * 8 + col; if (val) *m |= (1UL << index); else *m &= ~(1UL << index); } int get_bit(matrix_t m, int row, int col) { int index = row * 8 + col; return (m >> index) & 1; } int is_unholy(matrix_t m) { for (int i = 0; i < 64; i++) { int row = i / 8; int col = i % 8; if (get_bit(m, row, col)) { if ((row > 0 && get_bit(m, row - 1, col)) || (row < 7 && get_bit(m, row + 1, col)) || (col > 0 && get_bit(m, row, col - 1)) || (col < 7 && get_bit(m, row, col + 1))) continue; return 0; } } return 1; } int count_unholy(int rows) { if (rows == 0) return 1; int count = 0; for (matrix_t next_rows = 0; next_rows < (1UL << 16); next_rows++) { count += count_unholy(rows - 2); } return count; } int main() { int num_unholy = count_unholy(8); printf("Number of unholy 8x8 matrices: %d\n", num_unholy); return 0; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | #include <stdio.h> typedef unsigned long matrix_t; void set_bit(matrix_t *m, int row, int col, int val) { int index = row * 8 + col; if (val) *m |= (1UL << index); else *m &= ~(1UL << index); } int get_bit(matrix_t m, int row, int col) { int index = row * 8 + col; return (m >> index) & 1; } int is_unholy(matrix_t m) { for (int i = 0; i < 64; i++) { int row = i / 8; int col = i % 8; if (get_bit(m, row, col)) { if ((row > 0 && get_bit(m, row - 1, col)) || (row < 7 && get_bit(m, row + 1, col)) || (col > 0 && get_bit(m, row, col - 1)) || (col < 7 && get_bit(m, row, col + 1))) continue; return 0; } } return 1; } int count_unholy(int rows) { if (rows == 0) return 1; int count = 0; for (matrix_t next_rows = 0; next_rows < (1UL << 16); next_rows++) { count += count_unholy(rows - 2); } return count; } int main() { int num_unholy = count_unholy(8); printf("Number of unholy 8x8 matrices: %d\n", num_unholy); return 0; } |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | #include <stdio.h> typedef unsigned long matrix_t; void set_bit(matrix_t *m, int row, int col, int val) { int index = row * 8 + col; if (val) *m |= (1UL << index); else *m &= ~(1UL << index); } int get_bit(matrix_t m, int row, int col) { int index = row * 8 + col; return (m >> index) & 1; } int is_unholy(matrix_t m) { for (int i = 0; i < 64; i++) { int row = i / 8; int col = i % 8; if (get_bit(m, row, col)) { if ((row > 0 && get_bit(m, row - 1, col)) || (row < 7 && get_bit(m, row + 1, col)) || (col > 0 && get_bit(m, row, col - 1)) || (col < 7 && get_bit(m, row, col + 1))) continue; return 0; } } return 1; } int count_unholy(int rows) { if (rows == 0) return 1; int count = 0; for (matrix_t next_rows = 0; next_rows < (1UL << 16); next_rows++) { count += count_unholy(rows - 2); } return count; } int main() { int num_unholy = count_unholy(8); printf("Number of unholy 8x8 matrices: %d\n", num_unholy); return 0; } |
Timeout: function took too long to complete
Testing if the previous output contains the string 1121231537486377866
: False
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
Sure, here's a plan for the program: 1. **Define Constants and Data Structures** - Define constants for the matrix size (8x8) and the number of bits required to represent the matrix (64 bits). - Define an `unsigned long long` data type to represent the matrix (64 bits). 2. **Write the `is_unholy` Function** - Implement a function `is_unholy` that takes an `unsigned long long` matrix and returns `1` if the matrix is unholy (no isolated 1s), and `0` otherwise. - Use bit-shifting and masking operations to check for isolated 1s in the matrix. 3. **Implement the Dynamic Programming Solution** - Define a function `count_unholy_matrices` that takes the number of rows `n` and returns the count of unholy matrices with `n` rows. - Base case: If `n` is 0, return 1 (empty matrix is considered unholy). - Recursive case: - Enumerate all possible combinations of the next two rows (2^16 combinations). - For each combination, check if it is compatible with the previous rows (no isolated 1s at the boundary). - If compatible, recursively count the number of unholy matrices for the remaining rows and add it to the total count. - Use memoization (cache the results) to avoid redundant computations. 4. **Main Function** - In the `main` function, call the `count_unholy_matrices` function with `n=8` and print the result. Here's the C implementation:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | #include <stdio.h> #include <stdint.h> #define MATRIX_SIZE 8 #define MATRIX_BITS (MATRIX_SIZE * MATRIX_SIZE) // Cache for memoization unsigned long long memo[MATRIX_SIZE + 1]; // Check if a matrix is unholy int is_unholy(uint64_t matrix) { uint64_t mask = 0x8000000000000000; for (int i = 0; i < MATRIX_BITS; i++) { if (matrix & mask) { // Check if there are neighbors in cardinal directions uint64_t neighbors = (matrix & (mask << 1)) | (matrix & (mask >> 1)) | (matrix & (mask << MATRIX_SIZE)) | (matrix & (mask >> MATRIX_SIZE)); if (!neighbors) return 0; // Isolated 1 found, matrix is not unholy } mask >>= 1; } return 1; // No isolated 1s found, matrix is unholy } // Count the number of unholy matrices with n rows unsigned long long count_unholy_matrices(int n) { if (n == 0) return 1; // Empty matrix is considered unholy if (memo[n] != 0) return memo[n]; // Return cached result unsigned long long count = 0; uint64_t mask = (1ULL << (2 * MATRIX_SIZE)) - 1; // Mask for the next two rows for (uint64_t rows = 0; rows <= mask; rows++) { if (is_unholy(rows)) { count += count_unholy_matrices(n - 2); // Recurse for the remaining rows } } memo[n] = count; // Cache the result return count; } int main() { unsigned long long count = count_unholy_matrices(MATRIX_SIZE); printf("Number of unholy 8x8 matrices: %llu\n", count); return 0; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | #include <stdio.h> #include <stdint.h> #define MATRIX_SIZE 8 #define MATRIX_BITS (MATRIX_SIZE * MATRIX_SIZE) // Cache for memoization unsigned long long memo[MATRIX_SIZE + 1]; // Check if a matrix is unholy int is_unholy(uint64_t matrix) { uint64_t mask = 0x8000000000000000; for (int i = 0; i < MATRIX_BITS; i++) { if (matrix & mask) { // Check if there are neighbors in cardinal directions uint64_t neighbors = (matrix & (mask << 1)) | (matrix & (mask >> 1)) | (matrix & (mask << MATRIX_SIZE)) | (matrix & (mask >> MATRIX_SIZE)); if (!neighbors) return 0; // Isolated 1 found, matrix is not unholy } mask >>= 1; } return 1; // No isolated 1s found, matrix is unholy } // Count the number of unholy matrices with n rows unsigned long long count_unholy_matrices(int n) { if (n == 0) return 1; // Empty matrix is considered unholy if (memo[n] != 0) return memo[n]; // Return cached result unsigned long long count = 0; uint64_t mask = (1ULL << (2 * MATRIX_SIZE)) - 1; // Mask for the next two rows for (uint64_t rows = 0; rows <= mask; rows++) { if (is_unholy(rows)) { count += count_unholy_matrices(n - 2); // Recurse for the remaining rows } } memo[n] = count; // Cache the result return count; } int main() { unsigned long long count = count_unholy_matrices(MATRIX_SIZE); printf("Number of unholy 8x8 matrices: %llu\n", count); return 0; } |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | #include <stdio.h> #include <stdint.h> #define MATRIX_SIZE 8 #define MATRIX_BITS (MATRIX_SIZE * MATRIX_SIZE) // Cache for memoization unsigned long long memo[MATRIX_SIZE + 1]; // Check if a matrix is unholy int is_unholy(uint64_t matrix) { uint64_t mask = 0x8000000000000000; for (int i = 0; i < MATRIX_BITS; i++) { if (matrix & mask) { // Check if there are neighbors in cardinal directions uint64_t neighbors = (matrix & (mask << 1)) | (matrix & (mask >> 1)) | (matrix & (mask << MATRIX_SIZE)) | (matrix & (mask >> MATRIX_SIZE)); if (!neighbors) return 0; // Isolated 1 found, matrix is not unholy } mask >>= 1; } return 1; // No isolated 1s found, matrix is unholy } // Count the number of unholy matrices with n rows unsigned long long count_unholy_matrices(int n) { if (n == 0) return 1; // Empty matrix is considered unholy if (memo[n] != 0) return memo[n]; // Return cached result unsigned long long count = 0; uint64_t mask = (1ULL << (2 * MATRIX_SIZE)) - 1; // Mask for the next two rows for (uint64_t rows = 0; rows <= mask; rows++) { if (is_unholy(rows)) { count += count_unholy_matrices(n - 2); // Recurse for the remaining rows } } memo[n] = count; // Cache the result return count; } int main() { unsigned long long count = count_unholy_matrices(MATRIX_SIZE); printf("Number of unholy 8x8 matrices: %llu\n", count); return 0; } |
Number of unholy 8x8 matrices: 347131339034603841
Testing if the previous output contains the string 1121231537486377866
: False
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
A binary 8x8 matrix is 'unholy' if there are no isolated 1s. A 1 is isolated if there isn't another 1 in any of the 4 direct cardinal directions. Write a C program that counts the total number of unholy 8x8 matricies.To solve this question: - Use bit arithmetic and an unsigned long to represent the matrix. - Write a function is_unholy that tests if a matrix is unholy by bit-shifting and masking. Use a dynamic program to count the number of unholy matricies. - Recurse on the number of rows the matrix has. - Enumerate all 2^16 next two rows. This is enough to completely isolate the prior solutions from the next. Write out a plan for the program, and then implement the plan in C.
Sure, here's a plan for the program: 1. **Represent the matrix using an unsigned long integer** - Each bit in the unsigned long represents a cell in the 8x8 matrix. - Bit manipulation operations like shifting and masking can be used to check and modify the matrix. 2. **Define a function `is_unholy` to check if a matrix is unholy** - The function takes an unsigned long representing the matrix as input. - It checks each cell in the matrix to see if there is an isolated 1. - If an isolated 1 is found, the function returns 0 (false). - If no isolated 1 is found, the function returns 1 (true). 3. **Define a dynamic programming function `count_unholy` to count the number of unholy matrices** - The function takes an integer `n` representing the number of rows remaining in the matrix. - Base case: When `n` is 0, return 1 (as an empty matrix is considered unholy). - Recursive case: - Iterate over all possible combinations of the next two rows (2^16 combinations). - For each combination, recursively call `count_unholy` with `n-2` and add the result to a running total. - Return the running total. 4. **Implement the `is_unholy` function** - Use bit manipulation operations to check if a cell is isolated or not. - Check the cells above, below, to the left, and to the right of the current cell. - If any of the neighboring cells have a 1, the current cell is not isolated. 5. **Implement the `count_unholy` function** - Use the dynamic programming approach as described in step 3. - Utilize bit manipulation operations to generate all possible combinations of the next two rows. - Recursively call `count_unholy` for each combination and accumulate the results. 6. **Write the main function** - Call the `count_unholy` function with `n=8` (representing the entire 8x8 matrix). - Print the result. Here's the C implementation of the plan:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | #include <stdio.h> // Function to check if a matrix is unholy int is_unholy(unsigned long matrix) { unsigned long mask = 0x8040201008040201; // Mask for checking neighbors unsigned long isolated_mask = ~(mask | (mask << 1) | (mask >> 1)); // Mask for isolated cells // Check if there are any isolated 1s if ((matrix & isolated_mask) != 0) return 0; // Matrix is not unholy return 1; // Matrix is unholy } // Dynamic programming function to count the number of unholy matrices unsigned long count_unholy(int n) { if (n == 0) return 1; // Base case: an empty matrix is considered unholy unsigned long count = 0; // Iterate over all possible combinations of the next two rows for (unsigned long rows = 0; rows < (1UL << 16); rows++) { unsigned long matrix = rows << (64 - 16); // Shift rows to the top if (is_unholy(matrix)) count += count_unholy(n - 2); // Recursively count unholy matrices with n-2 rows } return count; } int main() { unsigned long count = count_unholy(8); printf("Number of unholy 8x8 matrices: %lu\n", count); return 0; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | #include <stdio.h> // Function to check if a matrix is unholy int is_unholy(unsigned long matrix) { unsigned long mask = 0x8040201008040201; // Mask for checking neighbors unsigned long isolated_mask = ~(mask | (mask << 1) | (mask >> 1)); // Mask for isolated cells // Check if there are any isolated 1s if ((matrix & isolated_mask) != 0) return 0; // Matrix is not unholy return 1; // Matrix is unholy } // Dynamic programming function to count the number of unholy matrices unsigned long count_unholy(int n) { if (n == 0) return 1; // Base case: an empty matrix is considered unholy unsigned long count = 0; // Iterate over all possible combinations of the next two rows for (unsigned long rows = 0; rows < (1UL << 16); rows++) { unsigned long matrix = rows << (64 - 16); // Shift rows to the top if (is_unholy(matrix)) count += count_unholy(n - 2); // Recursively count unholy matrices with n-2 rows } return count; } int main() { unsigned long count = count_unholy(8); printf("Number of unholy 8x8 matrices: %lu\n", count); return 0; } |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | #include <stdio.h> // Function to check if a matrix is unholy int is_unholy(unsigned long matrix) { unsigned long mask = 0x8040201008040201; // Mask for checking neighbors unsigned long isolated_mask = ~(mask | (mask << 1) | (mask >> 1)); // Mask for isolated cells // Check if there are any isolated 1s if ((matrix & isolated_mask) != 0) return 0; // Matrix is not unholy return 1; // Matrix is unholy } // Dynamic programming function to count the number of unholy matrices unsigned long count_unholy(int n) { if (n == 0) return 1; // Base case: an empty matrix is considered unholy unsigned long count = 0; // Iterate over all possible combinations of the next two rows for (unsigned long rows = 0; rows < (1UL << 16); rows++) { unsigned long matrix = rows << (64 - 16); // Shift rows to the top if (is_unholy(matrix)) count += count_unholy(n - 2); // Recursively count unholy matrices with n-2 rows } return count; } int main() { unsigned long count = count_unholy(8); printf("Number of unholy 8x8 matrices: %lu\n", count); return 0; } |
Number of unholy 8x8 matrices: 1048576
Testing if the previous output contains the string 1121231537486377866
: False