Leetcode 51 N-Queens

triplebee

发布于 2018-01-12 15:02:54

4840

发布于 2018-01-12 15:02:54

文章被收录于专栏：计算机视觉与深度学习基础计算机视觉与深度学习基础计算机视觉与深度学习基础

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.."]
]

N皇后问题

没有什么特别简单的方法，只能DFS

按行搜索，因而行不可能重复，只要判断列坐标和两者横纵坐标之差是否相等就行了。

class Solution {
public:
    bool judge(vector<int> col,int nowRow)
    {
        for(int i=0;i<nowRow;i++)
            if(col[i] == col[nowRow] || abs(col[nowRow]-col[i])==abs(i-nowRow)) return false;
        return true;
    }
    void dfs(vector<vector<string>> &result,int nowRow,vector<string> temp,vector<int> col)
    {
        int n=col.size();
        if(nowRow==n)
        {
            result.push_back(temp);
            return ;
        }
        temp.push_back(string(n,'.'));
        for(col[nowRow]=0;col[nowRow]<n;col[nowRow]++)
            if(judge(col,nowRow))
            {
                vector<string> temp2=temp;
                temp2[nowRow][col[nowRow]]='Q';
                dfs(result,nowRow+1,temp2,col);
            }
    }
    vector<vector<string>> solveNQueens(int n) 
    {
        vector<vector<string>> result;
        vector<string> temp;
        vector<int> col(n);
        dfs(result,0,temp,col);
        return result;
    }
};

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原始发表：2016-09-13 ，如有侵权请联系 cloudcommunity@tencent.com 删除

configuration