51. N-Queens | LeetCode Solution

 51. N-Queens | LeetCode Solution

The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.

Given an integer n, return all distinct solutions to the n-queens puzzle. You may return the answer in any order.

Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space, respectively.


Example 1:

Input: n = 4
Output: [[".Q..","...Q","Q...","..Q."],["..Q.","Q...","...Q",".Q.."]]
Explanation: There exist two distinct solutions to the 4-queens puzzle as shown above

Example 2:

Input: n = 1
Output: [["Q"]]



  • 1 <= n <= 9

class Solution {
    bool check(int r,int c,vector<string>&v,int n){
        for(int i=0; i<r; i++){
            if(v[i][c]=='Q')return false;
        int k=r;
        for(int i=r-1,j=c-1; i>=0 && j>=0 ; i--,j--){
            if(v[i][j]=='Q')return false;
        for(int i=r-1,j=c+1; i>=0 && j<n ; i--,j++){
            if(v[i][j]=='Q')return false;
        return true;
    void helper(int n, int row,int col,vector<string>&v){
        for(int i=col; i<n; i++){
    vector<vector<string>> solveNQueens(int n) {
        // res.push_back(ans);
        return res;

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