leetcode

0 class Solution {

1 public:

2 int reachNumber(int target) const {

3 target = abs(target);

4

5 const long long n = ceil((sqrt(1 + 8.0 * target) - 1.0) / 2);

6 const long long sum = n * (n + 1) / 2;

7

8 if (sum == target) return n;

9 const long long res = sum - target;

10

11 if (res % 2 == 0) return n;

12 return n + (n % 2 == 1) + 1;

13 }

14 };