[Leetcode] N-Queens

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.."]
]

Solution:
大神的做法：
http://blog.csdn.net/xift810/article/details/22187633

public class Solution {
    public List<String[]> solveNQueens(int n) {
    List<String[]> result = new ArrayList<String[]>();
        if (n == 0)
            return result;
        int[] rCol = new int[n];
        queens(result, rCol, 0, n);
        return result;
    }

    private void queens(List<String[]> result, int[] rCol, int row, int n) {
        // TODO Auto-generated method stub
        if (row == n) {
            printQueens(result, rCol, n);
            return;
        }
        for (int col = 0; col < n; ++col) {
            rCol[row] = col;
            if (check(rCol, row)) {
                queens(result, rCol, row + 1, n);
            }
        }
    }

    private boolean check(int[] rCol, int row) {
        // TODO Auto-generated method stub
        for (int i = 0; i < row; ++i) {
            if (rCol[i] == rCol[row])
                return false;
            if (Math.abs(row - i) == Math.abs(rCol[row] - rCol[i])) {
                return false;
            }
        }
        return true;
    }

    private void printQueens(List<String[]> result, int[] rCol, int n) {
        // TODO Auto-generated method stub
        String[] s = new String[n];
        for (int i = 0; i < n; ++i) {
            String temp = "";
            for (int j = 0; j < n; ++j) {
                if(rCol[i]==j){
                    temp+="Q";
                }else{
                    temp+=".";
                }
            }
            s[i]=temp;
        }
        result.add(s);
    }
}