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 {
public:
    int totalNumber=0;
    
    bool isValid(vector<int> layout, int recur)
    {
        for (int i=0; i<recur; ++i)
        {
            if (layout[i]==layout[recur]||layout[i]-layout[recur]==i-recur||layout[i]-layout[recur]==recur-i) 
              return false;
        }
        return true;
    }
    
    void helper(vector<int> layout,int recur, int n)
    {
        if (recur==n) totalNumber++;
        else
        {
            for (int i=0; i<n; ++i)
            {
                layout[recur]=i;
                if (isValid(layout,recur)) helper(layout,recur+1,n);
            }
        }
    }
    
    int totalNQueens(int n) {
        vector<int> layout(n,-1);
        helper(layout,0,n);
        return totalNumber;
    }
};


REMARK:
1. Easy version of the original problem N-Queens. Refer to the original problem.