LeetCode52:N-Queens II

Follow up for N-Queens problem.

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

和N-Queens 同样的解法。

class Solution {
public:
    int totalNQueens(int n) {
        vector<vector<string> > result;
        vector<int> nums;
        for(int i=0;i<n;i++)
            nums.push_back(i);
        vector<vector<int> > base=permutation(nums);
        return base.size();

    }

    vector<vector<int> > permutation(vector<int> &nums)
    {
        vector<vector<int> >result;
        permutationChild(nums,0,result);
        return result;
    }

    void permutationChild(vector<int> &nums,int offset,vector<vector<int> >&result)
    {

        if(offset==nums.size()-1)
        {
            if(judge(nums))
                result.push_back(nums);
            return;
        }

        auto base=nums.begin()+offset;
        auto iter=base;
        for(;iter!=nums.end();iter++)
        {
            swap(*base,*iter);
            permutationChild(nums,offset+1,result);
            swap(*base,*iter);
        }
    }

    bool judge(vector<int> & nums)
    {
        int length=nums.size();
        for(int i=0;i<length;i++)
        {
            for(int j=i+1;j<length;j++)
            {
                if(abs(i-j)==abs(nums[i]-nums[j]))
                    return false;
            }
        }

        return true;
    }
};