N-Queens N皇后放置问题 回溯法

N-Queens

 

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

Given an integer n, return all distinct solutions to the n-queens puzzle.

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

For example,
There exist two distinct solutions to the 4-queens puzzle:

[
 [".Q..",  // Solution 1
  "...Q",
  "Q...",
  "..Q."],

 ["..Q.",  // Solution 2
  "Q...",
  "...Q",
  ".Q.."]
]

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  Backtracking

class Solution {
public:
    vector > res;
    
    vector> solveNQueens(int n) {
        
        int *a=new int[n];
        memset(a,0,sizeof(int)*n);
        solve(a,n,0);
        return  res;
    }
    
    void solve(int *a, int n,int index)
    {
        for(int i=0;i path;
        for(int i=0;i