leetcode

0 class Solution {

1 public:

2 int pivotInteger(const int n) const {

3 int i = 1, j = n, l = 0, h = 0;

4 while (i < j) {

5 if (l < h)

6 l += i++;

7 else

8 h += j--;

9 }

10 return l == h ? i : -1;

11 }

12 };

13

14 class Solution {

15 public:

16 int pivotInteger(const int n) const {

17 const int sum = n * (n + 1) / 2;

18 const int pivot = sqrt(sum);

19 return pivot * pivot == sum ? pivot : -1;

20 }

21 };