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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.."] ]
class Solution { public: void init(vector<string> &temp, int n) { string strtemp(n,‘.‘); temp.insert(temp.end(),n,strtemp); return; } bool checkij(vector<string> &temp, int i, int j) { for (int ii=i-1,jleft=j-1;ii>=0&&jleft>=0;ii--,jleft--) { if(temp[ii][jleft]==‘Q‘)return false; } for (int ii=i-1,jright=j+1;ii>=0&&jright<temp.size();ii--,jright++) { if(temp[ii][jright]==‘Q‘)return false; } for (int k=0;k<temp.size();k++) { if (k!=j&&temp[i][k]==‘Q‘)return false; if (k!=i&&temp[k][j]==‘Q‘)return false; } return true; } bool solveOne(vector<vector<string>> &res,vector<string> &temp,int n, int index) { if(index==n) { res.push_back(temp); return true; } for (int j=0;j<n;j++) { temp[index][j]=‘Q‘; if (checkij(temp,index,j)) { solveOne(res,temp,n,index+1); } temp[index][j]=‘.‘; } } vector<vector<string>> solveNQueens(int n) { vector<vector<string>> res; vector<string> temp; init(temp,n); for(int i = 0; i < n; i++) { temp[0][i] = ‘Q‘; solveOne(res, temp, n, 1); temp[0][i] = ‘.‘; } return res; } };
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原文地址：http://www.cnblogs.com/Vae98Scilence/p/4283547.html
