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.
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 count the total number of "unholy" 8x8 binary matrices, where a matrix is defined as unholy if there are no isolated 1s (i.e., every `1` has at least one neighbor in the four cardinal directions: up, down, left, or right), we can use dynamic programming (DP) with bitmasking. ### Approach: 1. **Bitmask Representation:** - Each row of the matrix can be represented as an 8-bit number (`0` to `255`), where each bit denotes the presence (`1`) or absence (`0`) of a `1` in that position. 2. **Dynamic Programming State:** - **Current Row (`curr`):** The current row being processed. - **Previous Row (`prev`):** The row immediately above the current row. - **Valid State:** For each `1` in the `curr` row, there must be at least one adjacent `1` (left, right, or in the `prev` row). 3. **Transition:** - Iterate through all possible pairs of `prev` and `curr` rows. - For each pair, ensure that the `curr` row satisfies the unholy condition considering the `prev` row. - Use bitwise operations to efficiently check adjacency conditions. 4. **Initialization:** - Start with an initial state where the previous row is `0` (all `0`s). 5. **Final Count:** - After processing all rows, sum all valid configurations. ### Implementation: Below is a C program implementing the above approach. Due to the complexity of the state transitions and the need for efficiency, this program uses memoization and bitmask techniques to handle the large state space.
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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 | #include <stdio.h> #include <stdint.h> #include <stdlib.h> #include <string.h> // Number of possible states for a row #define STATES 256 // DP table size: 8 rows, STATES for previous row unsigned long long dp[8][STATES]; // Function to check if a given row is valid with respect to previous row int isValid(int prev, int curr) { // For each bit in the current row for(int i = 0; i < 8; i++) { if((curr & (1 << i)) != 0) { // Check left, right, and up int has_neighbor = 0; // Left neighbor if(i > 0 && (curr & (1 << (i-1)))) has_neighbor = 1; // Right neighbor if(i < 7 && (curr & (1 << (i+1)))) has_neighbor = 1; // Up neighbor if(prev & (1 << i)) has_neighbor = 1; if(!has_neighbor) return 0; // Isolated 1 found } } // Now check that in the previous row, any 1 has a neighbor in the current row for(int i = 0; i < 8; i++) { if((prev & (1 << i)) != 0) { int has_neighbor = 0; // Check up (which would be the row above prev, not tracked here, so skip) // Check left and right in prev if(i > 0 && (prev & (1 << (i-1)))) has_neighbor = 1; if(i < 7 && (prev & (1 << (i+1)))) has_neighbor = 1; // Check down (current row) if(curr & (1 << i)) has_neighbor = 1; if(!has_neighbor) return 0; // Isolated 1 in previous row } } return 1; } int main() { // Initialize DP memset(dp, 0, sizeof(dp)); // Initial state: no previous row // To handle the first row, previous row is 0 for(int curr = 0; curr < STATES; curr++) { // Check validity with prev = 0 // All 1s in current row must have a neighbor in the current row int valid = 1; for(int i = 0; i < 8; i++) { if((curr & (1 << i)) != 0) { int has_neighbor = 0; if(i > 0 && (curr & (1 << (i-1)))) has_neighbor = 1; if(i < 7 && (curr & (1 << (i+1)))) has_neighbor = 1; if(!has_neighbor) { valid = 0; break; } } } if(valid) { dp[0][curr] = 1; } } // Fill DP table for(int row = 1; row < 8; row++) { for(int prev = 0; prev < STATES; prev++) { if(dp[row-1][prev] == 0) continue; for(int curr = 0; curr < STATES; curr++) { if(isValid(prev, curr)) { dp[row][curr] += dp[row-1][prev]; } } } } // Now, we need to ensure that the last row's 1s are not isolated // Since there's no row below the last, check that last row's 1s have at least one neighbor in the row itself or in the previous row unsigned long long total = 0; for(int last = 0; last < STATES; last++) { // Validate last row with a virtual next row = 0 int valid = 1; // Check each 1 in the last row for(int i = 0; i < 8; i++) { if((last & (1 << i)) != 0) { int has_neighbor = 0; // Left if(i > 0 && (last & (1 << (i-1)))) has_neighbor = 1; // Right if(i < 7 && (last & (1 << (i+1)))) has_neighbor = 1; // Up (from previous row) // We need to check all possible previous rows that lead to this state // But in our DP, the dp[7][last] already includes valid transitions // So here, no need to check further if(!has_neighbor) { valid = 0; break; } } } if(valid) { total += dp[7][last]; } } printf("Total number of unholy 8x8 matrices: %llu\n", total); return 0; } |
1 2 | gcc -o count_unholy count_unholy.c ./count_unholy |
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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 | #include <stdio.h> #include <stdint.h> #include <stdlib.h> #include <string.h> // Number of possible states for a row #define STATES 256 // DP table size: 8 rows, STATES for previous row unsigned long long dp[8][STATES]; // Function to check if a given row is valid with respect to previous row int isValid(int prev, int curr) { // For each bit in the current row for(int i = 0; i < 8; i++) { if((curr & (1 << i)) != 0) { // Check left, right, and up int has_neighbor = 0; // Left neighbor if(i > 0 && (curr & (1 << (i-1)))) has_neighbor = 1; // Right neighbor if(i < 7 && (curr & (1 << (i+1)))) has_neighbor = 1; // Up neighbor if(prev & (1 << i)) has_neighbor = 1; if(!has_neighbor) return 0; // Isolated 1 found } } // Now check that in the previous row, any 1 has a neighbor in the current row for(int i = 0; i < 8; i++) { if((prev & (1 << i)) != 0) { int has_neighbor = 0; // Check up (which would be the row above prev, not tracked here, so skip) // Check left and right in prev if(i > 0 && (prev & (1 << (i-1)))) has_neighbor = 1; if(i < 7 && (prev & (1 << (i+1)))) has_neighbor = 1; // Check down (current row) if(curr & (1 << i)) has_neighbor = 1; if(!has_neighbor) return 0; // Isolated 1 in previous row } } return 1; } int main() { // Initialize DP memset(dp, 0, sizeof(dp)); // Initial state: no previous row // To handle the first row, previous row is 0 for(int curr = 0; curr < STATES; curr++) { // Check validity with prev = 0 // All 1s in current row must have a neighbor in the current row int valid = 1; for(int i = 0; i < 8; i++) { if((curr & (1 << i)) != 0) { int has_neighbor = 0; if(i > 0 && (curr & (1 << (i-1)))) has_neighbor = 1; if(i < 7 && (curr & (1 << (i+1)))) has_neighbor = 1; if(!has_neighbor) { valid = 0; break; } } } if(valid) { dp[0][curr] = 1; } } // Fill DP table for(int row = 1; row < 8; row++) { for(int prev = 0; prev < STATES; prev++) { if(dp[row-1][prev] == 0) continue; for(int curr = 0; curr < STATES; curr++) { if(isValid(prev, curr)) { dp[row][curr] += dp[row-1][prev]; } } } } // Now, we need to ensure that the last row's 1s are not isolated // Since there's no row below the last, check that last row's 1s have at least one neighbor in the row itself or in the previous row unsigned long long total = 0; for(int last = 0; last < STATES; last++) { // Validate last row with a virtual next row = 0 int valid = 1; // Check each 1 in the last row for(int i = 0; i < 8; i++) { if((last & (1 << i)) != 0) { int has_neighbor = 0; // Left if(i > 0 && (last & (1 << (i-1)))) has_neighbor = 1; // Right if(i < 7 && (last & (1 << (i+1)))) has_neighbor = 1; // Up (from previous row) // We need to check all possible previous rows that lead to this state // But in our DP, the dp[7][last] already includes valid transitions // So here, no need to check further if(!has_neighbor) { valid = 0; break; } } } if(valid) { total += dp[7][last]; } } printf("Total number of unholy 8x8 matrices: %llu\n", total); 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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 | #include <stdio.h> #include <stdint.h> #include <stdlib.h> #include <string.h> // Number of possible states for a row #define STATES 256 // DP table size: 8 rows, STATES for previous row unsigned long long dp[8][STATES]; // Function to check if a given row is valid with respect to previous row int isValid(int prev, int curr) { // For each bit in the current row for(int i = 0; i < 8; i++) { if((curr & (1 << i)) != 0) { // Check left, right, and up int has_neighbor = 0; // Left neighbor if(i > 0 && (curr & (1 << (i-1)))) has_neighbor = 1; // Right neighbor if(i < 7 && (curr & (1 << (i+1)))) has_neighbor = 1; // Up neighbor if(prev & (1 << i)) has_neighbor = 1; if(!has_neighbor) return 0; // Isolated 1 found } } // Now check that in the previous row, any 1 has a neighbor in the current row for(int i = 0; i < 8; i++) { if((prev & (1 << i)) != 0) { int has_neighbor = 0; // Check up (which would be the row above prev, not tracked here, so skip) // Check left and right in prev if(i > 0 && (prev & (1 << (i-1)))) has_neighbor = 1; if(i < 7 && (prev & (1 << (i+1)))) has_neighbor = 1; // Check down (current row) if(curr & (1 << i)) has_neighbor = 1; if(!has_neighbor) return 0; // Isolated 1 in previous row } } return 1; } int main() { // Initialize DP memset(dp, 0, sizeof(dp)); // Initial state: no previous row // To handle the first row, previous row is 0 for(int curr = 0; curr < STATES; curr++) { // Check validity with prev = 0 // All 1s in current row must have a neighbor in the current row int valid = 1; for(int i = 0; i < 8; i++) { if((curr & (1 << i)) != 0) { int has_neighbor = 0; if(i > 0 && (curr & (1 << (i-1)))) has_neighbor = 1; if(i < 7 && (curr & (1 << (i+1)))) has_neighbor = 1; if(!has_neighbor) { valid = 0; break; } } } if(valid) { dp[0][curr] = 1; } } // Fill DP table for(int row = 1; row < 8; row++) { for(int prev = 0; prev < STATES; prev++) { if(dp[row-1][prev] == 0) continue; for(int curr = 0; curr < STATES; curr++) { if(isValid(prev, curr)) { dp[row][curr] += dp[row-1][prev]; } } } } // Now, we need to ensure that the last row's 1s are not isolated // Since there's no row below the last, check that last row's 1s have at least one neighbor in the row itself or in the previous row unsigned long long total = 0; for(int last = 0; last < STATES; last++) { // Validate last row with a virtual next row = 0 int valid = 1; // Check each 1 in the last row for(int i = 0; i < 8; i++) { if((last & (1 << i)) != 0) { int has_neighbor = 0; // Left if(i > 0 && (last & (1 << (i-1)))) has_neighbor = 1; // Right if(i < 7 && (last & (1 << (i+1)))) has_neighbor = 1; // Up (from previous row) // We need to check all possible previous rows that lead to this state // But in our DP, the dp[7][last] already includes valid transitions // So here, no need to check further if(!has_neighbor) { valid = 0; break; } } } if(valid) { total += dp[7][last]; } } printf("Total number of unholy 8x8 matrices: %llu\n", total); return 0; } |
Total number of unholy 8x8 matrices: 5152918862634818
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.
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.
Certainly! Below is a C program that counts the total number of "unholy" 8x8 binary matrices. An "unholy" matrix is defined such that there are no isolated `1`s. A `1` is considered isolated if it doesn't have another `1` in any of the four direct cardinal directions (North, South, East, or West). ### Approach: To efficiently count the number of valid matrices without enumerating all \(2^{64}\) possibilities, we use **Dynamic Programming (DP)**. The idea is to process the matrix row by row, keeping track of the necessary constraints to ensure no `1` is isolated. **Key Points of the Approach:** 1. **State Representation:** - **`required` Mask:** For each row, we maintain a bitmask (`required`) that represents positions in the previous row that have `1`s requiring a neighboring `1` in the current row (to avoid isolation). 2. **Transition:** - For each possible configuration (`curr`) of the current row, we check: - **Satisfying `required` Constraints:** All positions marked in the `required` mask must have `1`s in the current row. - **Neighbor Constraints:** Every `1` in the current row must have at least one neighboring `1` either within the current row (left or right) or from the `required` mask (above). 3. **DP Table Update:** - If a configuration is valid, we update the DP table for the next row based on the current configuration. 4. **Final Calculation:** - After processing all rows, the final answer is the count of valid matrices where there are no pending `required` positions in the last row. ### C 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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | #include <stdio.h> #include <stdint.h> #include <string.h> int main(){ // Define DP arrays unsigned long long prev_dp[256]; unsigned long long current_dp[256]; // Initialize previous DP state: no required bits initially memset(prev_dp, 0, sizeof(prev_dp)); prev_dp[0] = 1; // Iterate over each row for(int row=0; row <8; row++){ // Reset current DP state memset(current_dp, 0, sizeof(current_dp)); // Iterate over all possible required masks from the previous row for(int required=0; required <256; required++){ if(prev_dp[required] == 0) continue; // Skip if no configurations lead to this state // Iterate over all possible current row configurations for(int curr=0; curr <256; curr++){ // Check if current configuration satisfies the required mask if( (required & ~curr) !=0 ) continue; // Required bits must be set in current row // Validate that every '1' in current row has at least one neighbor int valid = 1; for(int i=0; i<8; i++){ if(curr & (1 << i)){ int has_neighbor = 0; // Check left neighbor if(i >0 && (curr & (1 << (i-1)))) has_neighbor =1; // Check right neighbor if(i <7 && (curr & (1 << (i+1)))) has_neighbor =1; // Check upper neighbor if( (required & (1 <<i)) ) has_neighbor =1; if(!has_neighbor){ valid = 0; break; } } } if(valid){ int new_required; if(row <7){ // For rows 0 to 6, set new required bits based on current row new_required = curr; } else{ // For the last row, there are no rows below, so no required bits new_required = 0; } // Update the current DP state current_dp[new_required] += prev_dp[required]; } } } // Move to the next row memcpy(prev_dp, current_dp, sizeof(prev_dp)); } // The final answer is the number of configurations with no pending required bits printf("Total number of unholy 8x8 matrices: %llu\n", prev_dp[0]); return 0; } |
1 2 | gcc -o count_unholy_matrices count_unholy_matrices.c |
1 2 | ./count_unholy_matrices |
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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | #include <stdio.h> #include <stdint.h> #include <string.h> int main(){ // Define DP arrays unsigned long long prev_dp[256]; unsigned long long current_dp[256]; // Initialize previous DP state: no required bits initially memset(prev_dp, 0, sizeof(prev_dp)); prev_dp[0] = 1; // Iterate over each row for(int row=0; row <8; row++){ // Reset current DP state memset(current_dp, 0, sizeof(current_dp)); // Iterate over all possible required masks from the previous row for(int required=0; required <256; required++){ if(prev_dp[required] == 0) continue; // Skip if no configurations lead to this state // Iterate over all possible current row configurations for(int curr=0; curr <256; curr++){ // Check if current configuration satisfies the required mask if( (required & ~curr) !=0 ) continue; // Required bits must be set in current row // Validate that every '1' in current row has at least one neighbor int valid = 1; for(int i=0; i<8; i++){ if(curr & (1 << i)){ int has_neighbor = 0; // Check left neighbor if(i >0 && (curr & (1 << (i-1)))) has_neighbor =1; // Check right neighbor if(i <7 && (curr & (1 << (i+1)))) has_neighbor =1; // Check upper neighbor if( (required & (1 <<i)) ) has_neighbor =1; if(!has_neighbor){ valid = 0; break; } } } if(valid){ int new_required; if(row <7){ // For rows 0 to 6, set new required bits based on current row new_required = curr; } else{ // For the last row, there are no rows below, so no required bits new_required = 0; } // Update the current DP state current_dp[new_required] += prev_dp[required]; } } } // Move to the next row memcpy(prev_dp, current_dp, sizeof(prev_dp)); } // The final answer is the number of configurations with no pending required bits printf("Total number of unholy 8x8 matrices: %llu\n", prev_dp[0]); 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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | #include <stdio.h> #include <stdint.h> #include <string.h> int main(){ // Define DP arrays unsigned long long prev_dp[256]; unsigned long long current_dp[256]; // Initialize previous DP state: no required bits initially memset(prev_dp, 0, sizeof(prev_dp)); prev_dp[0] = 1; // Iterate over each row for(int row=0; row <8; row++){ // Reset current DP state memset(current_dp, 0, sizeof(current_dp)); // Iterate over all possible required masks from the previous row for(int required=0; required <256; required++){ if(prev_dp[required] == 0) continue; // Skip if no configurations lead to this state // Iterate over all possible current row configurations for(int curr=0; curr <256; curr++){ // Check if current configuration satisfies the required mask if( (required & ~curr) !=0 ) continue; // Required bits must be set in current row // Validate that every '1' in current row has at least one neighbor int valid = 1; for(int i=0; i<8; i++){ if(curr & (1 << i)){ int has_neighbor = 0; // Check left neighbor if(i >0 && (curr & (1 << (i-1)))) has_neighbor =1; // Check right neighbor if(i <7 && (curr & (1 << (i+1)))) has_neighbor =1; // Check upper neighbor if( (required & (1 <<i)) ) has_neighbor =1; if(!has_neighbor){ valid = 0; break; } } } if(valid){ int new_required; if(row <7){ // For rows 0 to 6, set new required bits based on current row new_required = curr; } else{ // For the last row, there are no rows below, so no required bits new_required = 0; } // Update the current DP state current_dp[new_required] += prev_dp[required]; } } } // Move to the next row memcpy(prev_dp, current_dp, sizeof(prev_dp)); } // The final answer is the number of configurations with no pending required bits printf("Total number of unholy 8x8 matrices: %llu\n", prev_dp[0]); return 0; } |
Total number of unholy 8x8 matrices: 478467
Testing if the previous output contains the string 1121231537486377866
: False