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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.."] ]
1 class Solution { 2 public: 3 vector<vector<string> > solveNQueens(int n) { 4 5 vector<int> q(n,-1); 6 vector<vector<string> > result; 7 getQueens(0,n,result,q); 8 return result; 9 } 10 11 void PrintQueens(vector<int> &q,vector<vector<string> > &result) 12 { 13 int n=q.size(); 14 vector<string> tmp; 15 string str; 16 for(int i=0;i<n;i++) 17 { 18 str=""; 19 for(int j=0;j<n;j++) 20 { 21 if(q[i]==j)str+=‘Q‘; 22 else str+=‘.‘; 23 } 24 tmp.push_back(str); 25 } 26 27 result.push_back(tmp); 28 } 29 30 void getQueens(int level,int &n,vector<vector<string> > &result,vector<int> &q) 31 { 32 if(level==n) 33 { 34 PrintQueens(q,result); 35 return; 36 } 37 bool flag=false; 38 for(int i=0;i<n;i++) 39 { 40 q[level]=i; 41 if(isValid(q,level)) 42 { 43 getQueens(level+1,n,result,q); 44 } 45 q[level]=-1; 46 } 47 } 48 49 bool isValid(vector<int> &q,int &level) 50 { 51 52 for(int i=0;i<level;i++) 53 { 54 if(q[i]==q[level]||abs(q[level]-q[i])==abs(level-i)) return false; 55 } 56 57 return true; 58 } 59 };
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原文地址：http://www.cnblogs.com/reachteam/p/4213979.html
