8_queen.c

#include<stdio.h>

void check(int*);

int success;

int main(void) {    

    int max = 8 * 8 * 8 * 8 * 8 * 8 * 8 * 8;
    int state = 0;
    
    //全ての配置を試行する 
    while (state < max) {
        int board[8] = {0};  
        int cur = state;

        int i = 0;
        while(i < 8) {
            board[i] = cur % 8;
            cur = cur / 8;
            ++i;
        }

        check(board);
        ++state;
    }
    
    printf("found %d answer(s).\n", success);
    return 0;
}

void check(int* board) {

    //横方向に衝突するコマが存在しないかどうか
    int yoko[8] = {0};
    int i = 0;
    
    while(i < 8) {
        if (yoko[board[i]]) {
            return; //衝突死 
        } else {
            yoko[board[i]] = 1;
        }
        ++i;
    }
    
    //左上,右下方面に衝突するコマが存在しないかどうか
    int left_upper[88] = {0};
    i = 0;
    while(i < 8) {
        int yoko = i;
        int tate = board[i];
        
        while (yoko * tate) {
            yoko = yoko - 1;
            tate = tate - 1;
        }
        
        if (left_upper[yoko * 10 + tate]) {        
            return; //衝突死 
        } else {
            left_upper[yoko * 10 + tate] = 1;    
        }
        ++i;
    }

    //左下,右上方面に衝突するコマが存在しないかどうか
    int right_upper[88] = {0};
    i = 0;
    while(i < 8) {
        int yoko = i;
        int tate = 7 - board[i];

        while (yoko * tate) {
            yoko = yoko - 1;
            tate = tate - 1;
        }

        if (right_upper[yoko * 10 + tate]) {
            return; //衝突死 
        } else {
            right_upper[yoko * 10 + tate] = 1;
        }   
        ++i;
    }

    i = 0;
    while(i < 8) {
        printf("%d ", board[i++]);
    }
    printf("\n");
    ++success;
}