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; } |
Okay, let's break down the function and golf it. **1. What the function does:** The function simulates a process on an 8x8 grid represented by a 64-bit unsigned integer (`unsigned long long`). 1. **Initialization:** It iterates through `1 << 16` (65536) possible starting configurations. Each configuration `i` (from 0 to 65535) determines the initial state of a specific 16-bit region within the 64-bit grid (`array` or `n`). The mapping seems to place the 16 bits of `i` into grid positions (bit indices) 9-12, 13-16, 17-20, and 21-24. 2. **Simulation Step:** For each initial state (`init` or `n`), it creates a copy (`array` or `a`). It then iterates through the *inner* cells of the 8x8 grid (rows 1 to 6, columns 1 to 6, corresponding to bit positions `p` where `1 <= p/8 <= 6` and `1 <= p%8 <= 6`). 3. **Rule Application:** For each inner cell `p`, it checks if the cell itself is '1' (`(a >> p) & 1`) and if all its direct neighbors (top `p-8`, left `p-1`, bottom `p+8`, right `p+1`) are '0'. If this condition is true (an isolated '1'), the cell `p` in the copied state `a` is set to '0'. 4. **Counting Stable States:** After checking all inner cells, it compares the final state `a` with the initial state `n`. If they are identical (meaning no cells were changed according to the rule), it increments a counter `c`. 5. **Return Value:** The function returns the final count `c`, representing the number of initial 16-bit configurations that are "stable" under one application of the rule. **2. Ways to make it shorter:** * **Remove Constants:** Replace `ROWS` and `COLS` with the literal `8`. (Already done in the provided snippet's logic, but good to note). * **Use Shorter Types/Names:** Use `int` where possible. Use single-letter variable names (`c`, `i`, `p`, `k`, `n`, `a`). Use `unsigned long long` for the 64-bit grid state, as it's shorter than `long long unsigned int`. Avoid includes like `<stdint.h>` if standard types suffice. * **Optimize Loops:** Combine nested loops into a single loop over relevant bit positions (`p`). Use the comma operator in `for` loops to combine initialization/increments. * **Optimize Bitwise Operations:** * Use bit shifts and masks efficiently to check neighbor states instead of extracting each one. The expression `!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1)` checks if all four neighbors are 0. * Use `1ULL` for 64-bit literal 1. * **Optimize Array Initialization:** The original calculation was complex. A loop or a more direct bit-shifting approach can be shorter. A loop iterating 4 times seems most concise. Use `15ULL` to ensure intermediate calculations are `unsigned long long`. * **Combine Conditionals:** Merge boundary checks (`p%8 && p%8<7`) with the cell/neighbor check into a single `if`. * **Remove Redundant Variables:** Use `a` directly for modification and compare with the initial `n`. * **Remove Whitespace and Braces:** Standard code golf practice. **3. Shortened Function:** Applying the optimizations:
1 2 3 4 5 | // Version using nested loops (closer to original structure) - approx 280 bytes int count(){int c=0,i,r,l,k,p;unsigned long long n,a;for(i=0;i<1<<16;i++){n=0;for(k=0;k<4;k++)n|=(i>>k*4&15ULL)<<(9+k*4);for(a=n,r=1;r<7;r++)for(l=1;l<7;l++){p=r*8+l;if((a>>p&1)&&!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1))a&=~(1ULL<<p);}c+=(n==a);}return c;} // Version using single loop for p - approx 268 bytes int count(){int c=0,i,k,p;unsigned long long n,a;for(i=0;i<1<<16;i++){n=0;for(k=0;k<4;k++)n|=(i>>k*4&15ULL)<<(9+k*4);for(a=n,p=9;p<55;p++)if(p%8>0&p%8<7){if((a>>p&1)&&!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1))a&=~(1ULL<<p);}c+=(n==a);}return c;} |
1 | int count(){int c=0,i,k,p;unsigned long long n,a;for(i=0;i<1<<16;i++){n=0;for(k=0;k<4;k++)n|=(i>>k*4&15ULL)<<(9+k*4);for(a=n,p=9;p<55;p++)if((p%8&&p%8<7)&&(a>>p&1)&&!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1))a&=~(1ULL<<p);c+=(n==a);}return c;} |
1 | int count(){int c=0,i,k,p;unsigned long long n,a;for(i=0;i<1<<16;i++){n=0;for(k=0;k<4;k++)n|=(i>>k*4&15ULL)<<(9+k*4);for(a=n,p=9;p<55;p++)if((p%8&&p%8<7)&&(a>>p&1)&&!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1))a&=~(1ULL<<p);c+=(n==a);}return c;} |
I extracted the following code from that output:
1 2 3 | #include <stdio.h> // Including a standard header as requested, though not strictly used by the function itself. int count(){int c=0,i,k,p;unsigned long long n,a;for(i=0;i<1<<16;i++){n=0;for(k=0;k<4;k++)n|=(i>>k*4&15ULL)<<(9+k*4);for(a=n,p=9;p<55;p++)if((p%8&&p%8<7)&&(a>>p&1)&&!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1))a&=~(1ULL<<p);c+=(n==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 | #include <stdio.h> // Including a standard header as requested, though not strictly used by the function itself. int count(){int c=0,i,k,p;unsigned long long n,a;for(i=0;i<1<<16;i++){n=0;for(k=0;k<4;k++)n|=(i>>k*4&15ULL)<<(9+k*4);for(a=n,p=9;p<55;p++)if((p%8&&p%8<7)&&(a>>p&1)&&!((a>>(p-8)|a>>(p-1)|a>>(p+8)|a>>(p+1))&1))a&=~(1ULL<<p);c+=(n==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 31376 instead of 27488.
Testing if the previous output contains the string All tests passed
: False
Resulting in output: False