N-Queens

Mar 20 '12

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.."]]

need improvement!

public class Solution {    public ArrayList
    
      solveNQueens(int n) {        // Start typing your Java solution below        // DO NOT write main() function        char[][] res = new char[n][n];        for(int i=0; i
     
       resList = new ArrayList
      
       ();                qRec(resList,res,board, 0);                //convert char[][] to ArrayList
       
        ;        return resList;    }        private void qRec(ArrayList
        
          resList, char[][] res, boolean[][] board ,int level){        int n = res.length;        if( level >= n) {            String[] ss = new String[n];            for(int i=0;i