Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
### Original Function Explanation The original function iterates through all 16-bit numbers, creating a 64-bit number `array` from each, where each 16-bit number is considered as a 4x4 grid of bits expanded into an 8x8 grid with empty cells around the original grid. The function then checks each cell in the original grid (ignoring the border) to see if it is set to 1 and all its immediate neighbors (top, left, bottom, right) are set to 0. If a cell meets these criteria, it is unset in `array`. Finally, if `array` remains unchanged after this process, the `count` is incremented. The function returns the total `count`. ### Optimization Steps 1. **Remove unnecessary variables**: ROWS and COLS are constants that can be hardcoded to reduce size. 2. **Simplify `array` calculation**: Simplify the bitwise operations used to create `array`. 3. **Combine loops**: The inner two loops can be combined into a single loop iteration over the relevant bits. 4. **Simplify conditions**: Simplify the logic used for checking neighbors and updating `array`. ### Shortened Function Given the steps described, here is an attempt to significantly shorten the function:
1 2 3 4 5 6 7 8 9 10 11 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long a = ((i&0xf)<<9)|((i&0xf0)<<13)|((i&0xf00)<<17)|((i&0xf000)<<21), t = a; for (int p = 9; p < 57; p+=8) for (int q = p; q < p + 4; q++) a &= ~((!((a >> (q-8) & 1) + (a >> (q+8) & 1) + (a >> (q-1) & 1) + (a >> (q+1) & 1)) & (a >> q & 1)) << q); c += (t == a); } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long a = ((i&0xf)<<9)|((i&0xf0)<<13)|((i&0xf00)<<17)|((i&0xf000)<<21), t = a; for (int p = 9; p < 57; p+=8) for (int q = p; q < p + 4; q++) a &= ~((!((a >> (q-8) & 1) + (a >> (q+8) & 1) + (a >> (q-1) & 1) + (a >> (q+1) & 1)) & (a >> q & 1)) << q); c += (t == a); } return c; } |
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 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long a = ((i&0xf)<<9)|((i&0xf0)<<13)|((i&0xf00)<<17)|((i&0xf000)<<21), t = a; for (int p = 9; p < 57; p+=8) for (int q = p; q < p + 4; q++) a &= ~((!((a >> (q-8) & 1) + (a >> (q+8) & 1) + (a >> (q-1) & 1) + (a >> (q+1) & 1)) & (a >> q & 1)) << q); c += (t == a); } return c; } #include<stdio.h> #include<stdlib.h> int main() { int answer = count(); int expected = 27488; if (answer != expected) { printf("Wrong answer; got %d instead of %d.\n", answer, expected); exit(1); } printf("All tests passed\n"); } |
All tests passed
Testing if the previous output contains the string All tests passed
: True
Resulting in output: True
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
### Explanation The function iterates over all possible 8x8 binary matrices (represented as a 64-bit integer) and counts how many of these matrices remain unchanged after making all cells that are '1' and have no '1' neighbors (top, bottom, left, right) into '0's, but only inside the inner 6x6 area (leaving the border unchanged). ### Shortening Strategy 1. **Loop Reduction**: Since the operation is symmetric and independent across the 64-bit space, we can loop directly over the relevant matrices without decomposing bits manually. 2. **Simplify Bit Manipulation**: We can simplify the bit manipulation by directly calculating the positions of the bits and using shifts and masks more efficiently. 3. **Direct Condition Checks**: Instead of manually checking each cell's neighbors, we can use bitwise operations to perform these checks more succinctly. ### Shortened Version
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long u = (i&0xf)<<9|(i&0xf0)<<21|(i&0xf00)<<33|(i&0xf000)<<45, v = u; for (int p = 9; p < 63; p++) u &= ((v >> p-9 | v >> p-1 | v >> p+1 | v >> p+9) & 1) << p | ~(1LL << p); c += u == v; } return c; } |
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long u = i&15<<9|i>>4&15<<21|i>>8&15<<33|i>>12<<45, v = u; for (int p = 9; p < 63; p++) u &= ((v >> p-9 | v >> p-1 | v >> p+1 | v >> p+9) & 1) << p | ~(1LL << p); c += u == v; } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long u = i&15<<9|i>>4&15<<21|i>>8&15<<33|i>>12<<45, v = u; for (int p = 9; p < 63; p++) u &= ((v >> p-9 | v >> p-1 | v >> p+1 | v >> p+9) & 1) << p | ~(1LL << p); c += u == v; } return c; } |
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 | int count() { int c = 0; for (int i = 0; i < 1 << 16; i++) { long long u = i&15<<9|i>>4&15<<21|i>>8&15<<33|i>>12<<45, v = u; for (int p = 9; p < 63; p++) u &= ((v >> p-9 | v >> p-1 | v >> p+1 | v >> p+9) & 1) << p | ~(1LL << p); c += u == v; } return c; } #include<stdio.h> #include<stdlib.h> int main() { int answer = count(); int expected = 27488; if (answer != expected) { printf("Wrong answer; got %d instead of %d.\n", answer, expected); exit(1); } printf("All tests passed\n"); } |
Wrong answer; got 20992 instead of 27488.
main.c: In function 'count':
main.c:5:50: warning: left shift count >= width of type [-Wshift-count-overflow]
5 | long long u = i&15<<9|i>>4&15<<21|i>>8&15<<33|i>>12<<45, v = u;
| ^~
main.c:5:60: warning: left shift count >= width of type [-Wshift-count-overflow]
5 | long long u = i&15<<9|i>>4&15<<21|i>>8&15<<33|i>>12<<45, v = u;
| ^~
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
1. **Explanation**: The function `count` traverses all 16-bit combinations to construct a 64-bit grid, represented by `array`. This grid is 8x8, but only the 4x4 central part (bits) is generated from the 16-bit input `i`. For each grid, it checks if any cell in the central 6x6 area (excluding the outermost border) is set (i.e., 1) and all its four direct neighbors (top, left, bottom, right) are unset (i.e., 0). If such a cell is found, it is unset. After checking all cells, if the grid remains unchanged, `count` is incremented. Essentially, it counts how many unique 4x4 configurations, when placed in the center of an 8x8 grid, do not have any cell that is set and isolated (surrounded by unset cells). 2. **Optimization Strategies**: - Remove unnecessary variables (`ROWS`, `COLS`). - Collapse the bitwise operations used to construct `array` into a more compact form. - Combine the loops or operations where possible. - Use shorter variable names. - Inline variable declarations and operations if they are used only once. - Avoid redundant calculations by directly incorporating constants and simplifying expressions. 3. **Shortened Function**:
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long long u = ((i & 0xf) << 9) | ((i & 0xf0) << 13) | ((i & 0xf00) << 17) | ((i & 0xf000) << 21), a = u; for (int p = 9; p < 56; p+=8) for (int q = p; q < p+4; q++) a &= ~(((a >> q & 1) && !((a >> (q - 1) & 1) | (a >> (q + 1) & 1) | (a >> (q - 8) & 1) | (a >> (q + 8) & 1))) << q); c += (u == a); } return c; } |
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long long u = ((i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21), a = u; for (int p = 9; p < 56; p+=8) for (int q = p; q < p+4; q++) a &= ~(((a >> q & 1) && !((a >> (q-1) | a >> (q+1) | a >> (q-8) | a >> (q+8)) & 1)) << q); c += (u == a); } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long long u = ((i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21), a = u; for (int p = 9; p < 56; p+=8) for (int q = p; q < p+4; q++) a &= ~(((a >> q & 1) && !((a >> (q-1) | a >> (q+1) | a >> (q-8) | a >> (q+8)) & 1)) << q); c += (u == a); } return c; } |
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 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long long u = ((i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21), a = u; for (int p = 9; p < 56; p+=8) for (int q = p; q < p+4; q++) a &= ~(((a >> q & 1) && !((a >> (q-1) | a >> (q+1) | a >> (q-8) | a >> (q+8)) & 1)) << q); c += (u == a); } return c; } #include<stdio.h> #include<stdlib.h> int main() { int answer = count(); int expected = 27488; if (answer != expected) { printf("Wrong answer; got %d instead of %d.\n", answer, expected); exit(1); } printf("All tests passed\n"); } |
All tests passed
Testing if the previous output contains the string All tests passed
: True
Resulting in output: True
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
1. **Explanation of the function's purpose**: The function `count` iterates through all 16-bit numbers, interpreting them as a 2D grid of 8x8 bits. For each configuration, it checks all cells (except those on the edges), and if a cell is set to 1 and all of its four neighboring cells (top, bottom, left, right) are 0, it clears that cell. After applying this rule to all cells, if the resulting grid is unchanged from the initial configuration, the function increments a counter. Finally, it returns the count of such unchanged configurations. 2. **Ways to shorten the function**: - Combine the constants `ROWS` and `COLS` as they are always equal and used in a context where their equality is essential. - Use fewer variables by combining expressions and removing unnecessary ones. - Utilize bitwise operations more efficiently and reduce redundant calculations. - Merge nested loops and conditions where possible. - Shorten variable names consistent with good coding practices in a code golf context. 3. **Shortened function**:
1 2 3 4 5 6 7 8 9 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned a = (i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21, t = a; for (int p = 9; p < 73; p+=(p%8==6)?3:1) a &= ~((t >> p & 1) && !(t >> (p-1) & 1) && !(t >> (p+1) & 1) && !(t >> (p-8) & 1) && !(t >> (p+8) & 1)) << p; c += (t == a); } return c; } |
1 2 3 4 5 6 7 8 9 10 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long a = (i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21, t = a; for (int p = 9; p < 73; p+=(p%8==6)?3:1) a &= ~((t>>p&1) && !(t>>(p-1)&1) && !(t>>(p+1)&1) && !(t>>(p-8)&1) && !(t>>(p+8)&1)) << p; c += (t == a); } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long a = (i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21, t = a; for (int p = 9; p < 73; p+=(p%8==6)?3:1) a &= ~((t>>p&1) && !(t>>(p-1)&1) && !(t>>(p+1)&1) && !(t>>(p-8)&1) && !(t>>(p+8)&1)) << p; c += (t == a); } return c; } |
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 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long a = (i & 0xf) << 9 | (i & 0xf0) << 13 | (i & 0xf00) << 17 | (i & 0xf000) << 21, t = a; for (int p = 9; p < 73; p+=(p%8==6)?3:1) a &= ~((t>>p&1) && !(t>>(p-1)&1) && !(t>>(p+1)&1) && !(t>>(p-8)&1) && !(t>>(p+8)&1)) << p; c += (t == a); } return c; } #include<stdio.h> #include<stdlib.h> int main() { int answer = count(); int expected = 27488; if (answer != expected) { printf("Wrong answer; got %d instead of %d.\n", answer, expected); exit(1); } printf("All tests passed\n"); } |
Wrong answer; got 16 instead of 27488.
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
Code golf this function to be a lot shorter. You only get points if it's <300 bytes (not counting whitespace). Keep the function named `count`.
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 | int count() { int ROWS = 8; int COLS = 8; int count = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int array = ((i & 0xf) << 9) | ((i & 0xf0) << (9 + 8 - 4)) | ((i & 0xf00) << (9 + 8 - 4 + 8 - 4)) | ((i & 0xf000) << (9 + 8 - 4 + 8 - 4 + 8 - 4)); long long unsigned int init = array; long long unsigned int temp = array; for (int i = 1; i < ROWS - 1; i++) { for (int j = 1; j < COLS - 1; j++) { // Calculate bit positions int pos = i * COLS + j; int topPos = (i - 1) * COLS + j; int leftPos = i * COLS + (j - 1); int bottomPos = (i + 1) * COLS + j; int rightPos = i * COLS + (j + 1); // Get the values of the neighbors int cell = (temp >> pos) & 1; int top = (temp >> topPos) & 1; int left = (temp >> leftPos) & 1; int bottom = (temp >> bottomPos) & 1; int right = (temp >> rightPos) & 1; // Sum the values of the neighbors int sum = top + left + bottom + right; // Update the cell if all neighbors are 0 and the cell itself is 1 if (sum == 0 && cell == 1) { array &= ~(1ULL << pos); } } } count += (init == array); } return count; } |
### Explanation The function `count` iterates over a 16-bit integer space, essentially examining configurations of a 4x4 grid (part of an 8x8 grid) for a particular condition: it checks if a cell that is initially set (1) remains unchanged when none of its four direct neighbors (top, left, bottom, right) are set. The count increases for each configuration where the initial setup equals the final setup, implying no cells were unset by the operation. This process involves bitwise operations to manipulate and check the grid's state efficiently. ### Simplification Steps 1. **Eliminate Unnecessary Variables:** The `ROWS` and `COLS` are constants and only used to define loop limits and calculate positions, which can be hardcoded for a 4x4 grid within an 8x8 grid. 2. **Combine Loops and Bitwise Operations:** The nested loops and the bitwise operations can be condensed by recognizing patterns in the positions' calculations and the condition for updating the count. 3. **Optimize Initialization of `array`:** The complex bitwise operations for initializing `array` can be simplified, considering the pattern and the fact that we're only interested in a 4x4 grid within an 8x8 grid. 4. **Inline Computations:** Inline computations for neighbors and removing the unnecessary temporary variable `temp` can reduce the code size. ### Reduced Function
1 2 3 4 5 6 7 8 9 10 11 | int count() { int c = 0; for (int i = 0; i < 1<<16; i++) { long long unsigned int a = ((i & 0xf) << 9) | ((i & 0xf0) << 12) | ((i & 0xf00) << 15) | ((i & 0xf000) << 18), b = a; for (int p = 9; p < 72; p+=8) for (int d = -9; d <= 9; d+=9) if (!(b & (7LL<<p))) a &= ~(1LL<<(p+d)); c += (a == b); } return c; } |
1 2 3 4 5 6 7 8 9 | int count() { int c=0; for (int i=0;i<1<<16;i++) { long long a=((i&0xf)<<9)|((i&0xf0)<<12)|((i&0xf00)<<15)|((i&0xf000)<<18),b=a; for (int p=9;p<72;p+=8) for (int d=-9;d<=9;d+=9) if (!(b&(7LL<<p))) a&=~(1LL<<(p+d)); c+=(a==b); } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 | int count() { int c=0; for (int i=0;i<1<<16;i++) { long long a=((i&0xf)<<9)|((i&0xf0)<<12)|((i&0xf00)<<15)|((i&0xf000)<<18),b=a; for (int p=9;p<72;p+=8) for (int d=-9;d<=9;d+=9) if (!(b&(7LL<<p))) a&=~(1LL<<(p+d)); c+=(a==b); } return c; } |
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 | int count() { int c=0; for (int i=0;i<1<<16;i++) { long long a=((i&0xf)<<9)|((i&0xf0)<<12)|((i&0xf00)<<15)|((i&0xf000)<<18),b=a; for (int p=9;p<72;p+=8) for (int d=-9;d<=9;d+=9) if (!(b&(7LL<<p))) a&=~(1LL<<(p+d)); c+=(a==b); } return c; } #include<stdio.h> #include<stdlib.h> int main() { int answer = count(); int expected = 27488; if (answer != expected) { printf("Wrong answer; got %d instead of %d.\n", answer, expected); exit(1); } printf("All tests passed\n"); } |
Wrong answer; got 5760 instead of 27488.
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True