【经典算法问题】素数环问题

/*素数环问题2014-4-8 17:22:28*/#include <stdio.h>#include <math.h>#include <string.h>bool hasSelected[21];int site[21];bool checkPrime(int k){if(k < 2) return 0;for(int i = 2; i <= sqrt(k); ++i)if(k % i == 0) return 0;return 1;}void print(){for(int i = 1; i < 21; ++i)printf("%d ", site[i]);printf("\n");}void backTrack(int k){if(k == 21){if(checkPrime(site[20] + site[1])) print();return;}int i, j;for(i = k; i < 21; ++i){for(j = 1; j < 21; ++j)if(!hasSelected[j] && checkPrime(j + site[k - 1])){ site[k] = j; hasSelected[j] = 1; backTrack(k + 1); hasSelected[j] = 0;}}}int main(){//freopen( "data.out", "w", stdout );site[1] = 1;hasSelected[1] = 1;backTrack(2);return 0;}