README.md

2485. Find the Pivot Integer

Given a positive integer n, find the pivot integerx 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 integerx. 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. 

Constraints:

• 1 <= n <= 1000

Solutions (Rust)

1. Solution

implSolution{pubfnpivot_integer(n:i32) -> i32{let x = ((n *(n + 1) / 2)asf64).sqrt()asi32;if x * x *2 == n *(n + 1){ x }else{ -1}}}