1. 记录下棋盘的内容 慢一些

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;
const int N = 15, M = 30;
char g[N][N];
// 直接记录答案也行
int path[N];
bool col[N], dg[M], ndg[M];
int n;
int num;

void dfs(int r){
    if (r == n + 1){
        num ++ ;
        if (num <= 3){
            for (int i = 1; i <= n; i ++ )
                for (int j = 1; j <= n; j ++ )
                    if (g[i][j] == '#') cout << j << ' ';
            cout << endl;
        }
        return;
    }
    for (int i = 1; i <= n; i ++ ){
        if (!col[i] && !dg[r + i] && !ndg[n + r - i]){
            col[i] = dg[r + i] = ndg[n + r - i] = true;
            g[r][i] = '#';
            dfs(r + 1);
            col[i] = dg[r + i] = ndg[n + r - i] = false;
            g[r][i] = '.';
        }
    }
}

int main(){
    cin >> n;
    for (int i = 1; i <= n; i ++ )
        for (int j = 1; j <= n; j ++ )
            g[i][j] = '.';

    dfs(1);
    printf("%d\n", num);
    return 0;
}

直接记录答案

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;
const int N = 15, M = 30;
int path[N];
bool col[N], dg[M], ndg[M];
int n;
int num;

void dfs(int r){
    if (r == n + 1){
        num ++ ;
        if (num <= 3){
            for (int i = 1; i <= n; i ++ )
                cout << path[i] << ' ';
            cout << endl;
        }
        return;
    }
    // 当行数r确定，遍历列数i
    for (int i = 1; i <= n; i ++ ){
        if (!col[i] && !dg[r + i] && !ndg[n + r - i]){
            col[i] = dg[r + i] = ndg[n + r - i] = true;
            path[r] = i;
            dfs(r + 1);
            col[i] = dg[r + i] = ndg[n + r - i] = false;
            path[r] = 0;
        }
    }
}

int main(){
    cin >> n;
    dfs(1);
    printf("%d\n", num);
    return 0;
}