Leetcode-996 Number of Squareful Arrays(正方形数组的数目)

#define _for(i,a,b) for(int i = (a);i < (b);i ++)
class Solution
{
    public:
        bool judge(int n)
        {
            if(n == (int)sqrt(n)*(int)sqrt(n))
                return true;
            return false;
        }
        int numSquarefulPerms(vector<int>& A)
        {
            int sz = A.size();
            int cnt = 0;
            int p = 0;
            _for(i,0,sz)
                _for(j,i+1,sz)
                    if(judge(A[i]+A[j]))
                        p ++;
            if(p*2<sz)
                return 0;
            sort(A.begin(),A.end());
            do
            {
                int i;
                for(i = 0;i < sz-1;i ++)
                    if(!judge(A[i]+A[i+1]))
                        break;
                if(i==sz-1)
                    cnt ++;
            }
            while(next_permutation(A.begin(),A.end()));
            return cnt;
        }
};

 暴力+优化，说实话能过我也觉得很奇妙，可能是因为数据范围很小的缘故吧