n皇后问题c++变形

以下是一个C++实现的n皇后问题的变形，使用深度优先搜索（DFS）算法：

#include <iostream>
#include <vector>

using namespace std;

// 判断当前位置是否可以放置皇后
bool isValid(vector<int>& queens, int row, int col) {
    for (int i = 0; i < row; i++) {
        // 判断是否在同一列或同一斜线上
        if (queens[i] == col || queens[i] - col == i - row || queens[i] - col == row - i) {
            return false;
        }
    }
    return true;
}

// 深度优先搜索
void dfs(vector<vector<string>>& res, vector<int>& queens, int row, int n) {
    if (row == n) {
        // 生成棋盘
        vector<string> board(n, string(n, '.'));
        for (int i = 0; i < n; i++) {
            board[i][queens[i]] = 'Q';
        }
        res.push_back(board);
        return;
    }
    
    for (int col = 0; col < n; col++) {
        if (isValid(queens, row, col)) {
            queens[row] = col;
            dfs(res, queens, row + 1, n);
        }
    }
}

vector<vector<string>> solveNQueens(int n) {
    vector<vector<string>> res;
    vector<int> queens(n, -1);
    dfs(res, queens, 0, n);
    return res;
}

int main() {
    int n = 4;
    vector<vector<string>> res = solveNQueens(n);
    
    // 输出结果
    for (int i = 0; i < res.size(); i++) {
        cout << "Solution " << i + 1 << ":" << endl;
        for (int j = 0; j < n; j++) {
            cout << res[i][j] << endl;
        }
        cout << endl;
    }
    
    return 0;
}