LeetCode 101 N-Queens II

Follow up for N-Queens problem.

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

分析：

这和上一题没有本质区别，只是把上一题的打印棋盘变成结果加1，所以准确来讲还简单一些，需要一个类变量来存储结果。

public class Solution {
    int res;
    public int totalNQueens(int n) {
        res = 0;
        if(n < 0) return res;
        int[] loc = new int[n];
        dfs(loc, 0, n);
        return res;
    }
    public void dfs(int[] loc, int cur, int n){
        if(cur == n){
            res++;
            return;
        }
        for(int i=0; i<n; i++){
            loc[cur] = i;
            if(isValid(loc, cur))
                dfs(loc, cur+1, n);
        }
    }
    
    public boolean isValid(int[] loc, int cur){
        for(int i=0; i<cur; i++){
            if(loc[i]==loc[cur] || Math.abs(loc[i]-loc[cur])==(cur-i))
                return false;
        }
        return true;
    }
}