LeetCode OJ:N-Queens II

N-Queens II

 

Follow up for N-Queens problem.

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

class Solution {
    vector<bool> row,col,lslash,rslash;
    int result;
public:
    void dfs(int deep,int n){
        if(deep==n){
            result++;
            return;
        }
        for(int i=0;i<n;i++){
            if(!row[deep]&&!col[i]&&!lslash[deep+i]&&!rslash[deep+n-1-i]){
                row[deep]=col[i]=lslash[deep+i]=rslash[deep+n-1-i]=true;
                dfs(deep+1,n);
                row[deep]=col[i]=lslash[deep+i]=rslash[deep+n-1-i]=false;
            }
        }
    }
    int totalNQueens(int n) {
        row.assign(n,false);//某行是否有皇后了
        col.assign(n,false);//某列是否有皇后了
		lslash.assign(2*n,false);//左斜线是否有皇后了
		rslash.assign(2*n,false);//右斜线是否有皇后了
        result=0;
        dfs(0,n);
        return result;
    }
};