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// Solution for http://haskell98.blogspot.ru/2014/10/blog-post_10.html | |
// Results at http://haskell98.blogspot.ru/2014/10/blog-post_20.html | |
#include <stdlib.h> | |
#include <stdio.h> | |
#include <stdbool.h> | |
typedef unsigned long long int bigint; | |
static int mask(int n, int i, int j) { | |
if (i < n && j < n) { | |
return 0; | |
} else if (i < n && j >= n) { | |
return 1; | |
} else if (i >= n && j < n) { | |
return 2; | |
} else { | |
return 3; | |
} | |
} | |
static int shift(int n, int i, int j) { | |
int ii, jj; | |
if (i < n && j < n) { | |
ii = i; | |
jj = j; | |
} else if (i < n && j >= n) { | |
ii = (2*n - j - 1); | |
jj = i; | |
} else if (i >= n && j < n) { | |
ii = j; | |
jj = (2*n - i - 1); | |
} else { | |
ii = (2*n - i - 1); | |
jj = (2*n - j - 1); | |
} | |
return 2 * (ii*n + jj - 1); | |
} | |
static bool is_a_hole(int n, int i, int j, bigint x) { | |
if ((i == 0 || i == 2*n - 1) && (j == 0 || j == 2*n - 1)) { | |
// hole is in the left top corner | |
return i == 0 && j == 0; | |
} else { | |
int check = mask(n, i, j); | |
x >>= shift(n, i, j); | |
x &= 3; | |
return x == check; | |
} | |
} | |
int main(int argc, char *argv[]) { | |
if (argc != 2) { | |
fprintf(stderr, "Usage: %s <n>\n", argv[0]); | |
return 1; | |
} | |
int n = atoi(argv[1]); | |
bigint count = 1; | |
count <<= 2 * (n*n - 1); | |
printf("Number of variants: %lli\n", count); | |
for (bigint x = 0; x < count; x++) { | |
putchar('\n'); | |
for (int i = 0; i < 2*n; ++i) { | |
for (int j = 0; j < 2*n; ++j) { | |
putchar(is_a_hole(n, i, j, x) ? 'O' : '_'); | |
putchar(' '); | |
} | |
putchar('\n'); | |
} | |
} | |
return 0; | |
} |
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