【leetcode】 N-Queens

地址

https://leetcode.com/problems/n-queens/description/

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. 'one solution to the eight queens puzzle' 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.."]]

思路

傻逼暴力题,居然还是hard

代码

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class Solution {
public:
int n,ul[100],ux[100],uy[100];
char mp[100][100];
vector<vector<string>> ans;
vector<string>tmp;

void dfs(int x)
{
if(x==n)
{
tmp.clear();
for(int i=0;i<n;i++)
{
string tb;
for(int j=0;j<n;j++)
tb+=mp[i][j];
cout<<tb<<endl;
tmp.push_back(tb);
}
ans.push_back(tmp);
cout<<endl;
return ;
}
for(int j=0;j<n;j++)
if(ul[j]==0&&ux[j-x+50]==0&&uy[n-x-j+50]==0)
{
ul[j]=ux[j-x+50]=uy[n-x-j+50]=1;
mp[x][j]='Q';
dfs(x+1);
mp[x][j]='.';
ul[j]=ux[j-x+50]=uy[n-x-j+50]=0;
}
}
vector<vector<string>> solveNQueens(int N) {
n=N;
memset(ul,0,sizeof ul);
memset(ux,0,sizeof ux);
memset(uy,0,sizeof uy);
for(int i=0;i<n;i++)
for(int j=0;j<n;j++)
mp[i][j]='.';
dfs(0);
return ans;
}
};