#2485
Find the Pivot Integer
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Description
Given a positive integer n, find the pivot integer x such that:
- The sum of all elements between 1 and x inclusively equals the sum of all elements between x and n inclusively.
Return the pivot integer x. If no such integer exists, return -1. It is guaranteed that there will be at most one pivot index for the given input.
Example 1:
Input: n = 8
Output: 6
Explanation: 6 is the pivot integer since: 1 + 2 + 3 + 4 + 5 + 6 = 6 + 7 + 8 = 21.
Example 2:
Input: n = 1
Output: 1
Explanation: 1 is the pivot integer since: 1 = 1.
Example 3:
Input: n = 4
Output: -1
Explanation: It can be proved that no such integer exist.
Solution