#include<iostream> #include<vector> #include<math.h> #include<stdio.h> using namespace std; int temp = 0; int place(int k, vector<int>& x) { for (int i = 1; i < k; i++) if (x[k] == x[i] || fabs(k - i) == fabs(x[k] - x[i])) return 1; return 0; }int queens(int i, vector<int>&x,int n) { if (i > n) { #if 0 for (int k = 1; k <= n; k++) cout << x[k]; cout << "\n"; #endif } else for (int j = 1; j <= n; j++) { x[i] = j; if (place(i, x) == 0) queens(i + 1, x, n); } } int main() { int z; cin >> z; int n; for (int i = 1; i <= z; i++) { cin >> n; vector<int>x(n + 1); int begin = clock(); int flag = queens(1, x, n); int end = clock(); cout << flag; cout << "\n"; } }以上代码要求增加输出解的个数

可以在 queens 函数中增加一个计数器，记录找到的解的个数，然后在 main 函数中输出即可。修改后的代码如下：

#include<iostream> 
#include<vector> 
#include<math.h> 
#include<stdio.h> 

using namespace std; 

int temp = 0; 

int place(int k, vector<int>& x) { 
    for (int i = 1; i < k; i++) 
        if (x[k] == x[i] || fabs(k - i) == fabs(x[k] - x[i])) 
            return 1; 
    return 0; 
}

int queens(int i, vector<int>& x, int n, int& count) { 
    if (i > n) { 
#if 0 
        for (int k = 1; k <= n; k++) 
            cout << x[k]; 
        cout << "\n"; 
#endif 
        count++; // 找到一个解，计数器加一 
    } else {
        for (int j = 1; j <= n; j++) { 
            x[i] = j; 
            if (place(i, x) == 0) 
                queens(i + 1, x, n, count); 
        } 
    }
    return count;
} 

int main() { 
    int z; 
    cin >> z; 
    int n; 
    for (int i = 1; i <= z; i++) { 
        cin >> n; 
        vector<int> x(n + 1); 
        int begin = clock(); 
        int count = 0; // 初始化计数器 
        queens(1, x, n, count); 
        int end = clock(); 
        cout << count << "\n"; // 输出解的个数 
    } 
    return 0;
}