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; } |
# Understanding the Function This function: 1. Iterates over all possible 16-bit numbers (0 to 65535) 2. For each number, creates a 64-bit array by spreading bits into specific positions 3. Applies a cellular automaton rule: if a cell is 1 and all its neighbors (top, left, bottom, right) are 0, the cell becomes 0 4. Counts how many configurations remain unchanged after applying the rule once # Ways to Shorten 1. Simplify the array initialization by using a more direct bit mapping formula 2. Eliminate unnecessary variables and combine operations 3. Replace the nested loops with direct bit operations on specific positions 4. Use precomputed masks for the positions to check 5. Use bitwise operations to check neighbors more efficiently # Golf Implementation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0,t; for(int j=0;j<4;j++)a|=((i>>(j*4))&15)<<(9+j*4); t=a; for(int r=1;r<7;r++) for(int c=1;c<7;c++){ int p=r*8+c; if((t>>p)&1&&!((t>>(p-1))&1)&&!((t>>(p-8))&1)&&!((t>>(p+1))&1)&&!((t>>(p+8))&1)) a&=~(1ULL<<p); } c+=a==t; } return c; } |
1 2 3 4 5 6 7 8 9 10 11 12 13 | int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>(j*4))&15)<<(9+j*4); long long t=a; for(int p=9;p<55;p++) if(p%8>0&&p%8<7&&(t>>p)&1&&!((t>>(p-1))&1)&&!((t>>(p-8))&1)&&!((t>>(p+1))&1)&&!((t>>(p+8))&1)) a&=~(1ULL<<p); c+=a==t; } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | #include <stdio.h> int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>(j*4))&15)<<(9+j*4); long long t=a; for(int p=9;p<55;p++) if(p%8>0&&p%8<7&&(t>>p)&1&&!((t>>(p-1))&1)&&!((t>>(p-8))&1)&&!((t>>(p+1))&1)&&!((t>>(p+8))&1)) a&=~(1ULL<<p); c+=a==t; } 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 29 30 31 32 | #include <stdio.h> int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>(j*4))&15)<<(9+j*4); long long t=a; for(int p=9;p<55;p++) if(p%8>0&&p%8<7&&(t>>p)&1&&!((t>>(p-1))&1)&&!((t>>(p-8))&1)&&!((t>>(p+1))&1)&&!((t>>(p+8))&1)) a&=~(1ULL<<p); c+=a==t; } 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 31376 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; } |
# Understanding the Function This function is counting how many of the 65,536 possible 16-bit numbers remain unchanged after a specific transformation. The transformation: 1. The 16-bit number is expanded into a 64-bit value representing an 8x8 grid 2. For each cell in the grid (excluding the border), if the cell is 1 AND all four adjacent neighbors (top, left, right, bottom) are 0, then the cell is set to 0 3. If the resulting grid matches the original grid, we increment the counter # Optimization Approach I'll make this shorter by: 1. Using shorter variable names 2. Simplifying the array initialization with a loop 3. Combining the nested loops and conditions 4. Using `long long` instead of `long long unsigned int` 5. Using bitwise operators more efficiently 6. Removing unnecessary parentheses where possible # Shortened Solution
1 2 3 4 5 6 7 8 9 10 11 12 13 | int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>j*4)&15)<<(9+j*8); long long o=a; for(int p=9;p<55;p++) if(p%8&&p%8<7&&(a>>p)&1&&!(((a>>(p-8))&1)|((a>>(p-1))&1)|((a>>(p+1))&1)|((a>>(p+8))&1))) o&=~(1LL<<p); c+=(a==o); } return c; } |
1 2 3 4 5 6 7 8 9 10 11 12 13 | int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>j*4)&15)<<(9+j*8); long long o=a; for(int p=9;p<55;p++) if(p%8&&p%8<7&&(a>>p)&1&&!(((a>>(p-8))&1)|((a>>(p-1))&1)|((a>>(p+1))&1)|((a>>(p+8))&1))) o&=~(1LL<<p); c+=(a==o); } return c; } |
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | #include <stdint.h> int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>j*4)&15)<<(9+j*8); long long o=a; for(int p=9;p<55;p++) if(p%8&&p%8<7&&(a>>p)&1&&!(((a>>(p-8))&1)|((a>>(p-1))&1)|((a>>(p+1))&1)|((a>>(p+8))&1))) o&=~(1LL<<p); c+=(a==o); } 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 29 30 31 32 | #include <stdint.h> int count(){ int c=0; for(int i=0;i<1<<16;i++){ long long a=0; for(int j=0;j<4;j++)a|=((i>>j*4)&15)<<(9+j*8); long long o=a; for(int p=9;p<55;p++) if(p%8&&p%8<7&&(a>>p)&1&&!(((a>>(p-8))&1)|((a>>(p-1))&1)|((a>>(p+1))&1)|((a>>(p+8))&1))) o&=~(1LL<<p); c+=(a==o); } 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 32400 instead of 27488.
Testing if the previous output contains the string All tests passed
: False
Resulting in output: True