【LeetCode】051. N-Queens

题目：

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.."]

]

题解：

class Solution {

public:

    void dfs(vector<vector<string>>& res, vector<string>& v, int n, vector<int>& pos, int row) {

         if(row >= n) {

             res.push_back(v);

             return;

         }

         for(int col=; col<n; ++col) {

            if (!isValid(pos, row, col)) {

                continue;

            }

            v[row][col] = 'Q';

            pos[row] = col;

            dfs(res, v, n, pos, row + );

            pos[row] = -;

            v[row][col] = '.';

         }

    }

    bool isValid(vector<int>& pos, int row, int col) {

        for (int i = ; i < row; ++i) {

            if (pos[i] == col || abs(row - i) == abs(col - pos[i])) {

                return false;

            }

        }

        return true;

    }

    vector<vector<string>> solveNQueens(int n) {

        vector<vector<string>> res;

        vector<string> v(n, string(n, '.'));

        vector<int> pos(n, -);

        dfs(res, v, n, pos, );

        return res;

    }

};

巴特西

【LeetCode】051. N-Queens

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