Created
December 11, 2013 16:48
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N Queens Problem (N <= 16)
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//compile with -Ofast -march=native -funroll-loops | |
#include <stdio.h> | |
typedef unsigned short uint16_t; | |
template <int n, int m> | |
struct queens { | |
static void f(uint16_t col, uint16_t left, uint16_t right, size_t& count) { | |
uint16_t mask = ~(col | left | right); | |
for (int i = 0; i < n; ++i, mask >>= 1) { | |
if (! mask) return; | |
if (mask & 1) { | |
queens<n, m-1>::f(col | (1 << i), (left >> 1) | (1 << (i-1)), (right << 1) | (1 << (i + 1)), count); | |
} | |
} | |
} | |
}; | |
template <int n> | |
struct queens<n, 0> { | |
static void f(uint16_t, uint16_t, uint16_t, size_t& count) { ++count; } | |
}; | |
int main(int, const char *[]) | |
{ | |
size_t count = 0; | |
queens<16, 16>::f(0, 0, 0, count); | |
printf("%lu\n", count); | |
return 0; | |
} |
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