Cycle 8 queens

This will not cause stack explosion, but the efficiency is very low. The time complexity of O (N ^ 2) needs to be optimized.

#include <stdio.h>#define N 10int q[N+1] = {0};int cnt = 0;void print_q() {    int i;    for (i=0; i<N; i++) printf("%d ", q[i]);    printf("\n");    return;}int can_put(int m, int n) {    int i,j;    //row is ok    //colume    for (i=0; i<m; i++) {        if (q[i] == n) return 0;    }    //left-up    for (i=m-1,j=n-1; i>=0 && j>=0; i--,j--) {        if (q[i] == j) return 0;    }    //right-up    for (i=m-1,j=n+1; i>=0 && j<N; i--,j++) {        if (q[i] == j) return 0;    }    return 1;}void next_qn() {    int i=0;    while (i <= N) {        if (q[i] < N-1) {            q[i] +=1;            break;        }        q[i] = 0;        i++;    }    return;}int main(int argc, char* argv[]) {    while (q[N] == 0) {        int i;        for (i=0; i<N; i++) {            if (!can_put(i, q[i])) break;        }        if (i == N) {            cnt++;            print_q();        }        next_qn();    }    printf("CNT: %d\n", cnt);    return 0;}

 

Cycle 8 queens