leetcode

0 class Solution {

1 public:

2 int maxValue(int n, int index, int maxSum) {

3 const int a = index, b = n - index - 1;

4 int low = 0, high = maxSum;

5

6 const auto arit = [](long n, int mid) { return (long)n * mid - n * (n + 1) / 2; };

7 while (low < high) {

8 int mid = (low + high + 1) / 2;

9 long res = mid + arit(min(a, mid - 1), mid) + arit(min(b, mid - 1), mid);

10 if (res <= maxSum - n)

11 low = mid;

12 else

13 high = mid - 1;

14 }

15 return low + 1;

16 }

17 };