[leetcode]N-QueensII

N-Queens II

Follow up for N-Queens problem.

Now, instead outputting board configurations, return the total number of distinct solutions.

 

算法思路：

与[leetcode]N-Queens完全一样，不过更简单，只统计个数即可。

代入如下：

public class Solution {
    int count = 0;
    public int totalNQueens(int n) {
        if(n < 1) return 0;
        int[] hash = new int[n];
        dfs(hash,0,n);
        return count;
    }
    private void dfs(int[] hash,int row,int n){
        if(row == n){
            count++;
            return;
        }
        for(int i = 0; i < n; i++){
            if(!isConflict(hash,row,i)){
                hash[row] = i;
                dfs(hash, row + 1, n);
                hash[row] = 0;
            }
        }
    }
    private boolean isConflict(int[] hash,int row,int column){
        for(int i = 0; i < row; i++){
            if(hash[i] == column || i - hash[i] == row - column || i + hash[i] == row + column) return true;
        }
        return false;
    }
}