Count partitions with even sum difference

Array Math Prefix Sum

85.2% acceptance

Feb 25, 2026

403

You are given an integer array nums of length n. A partition is defined as an index i where 0 <= i < n - 1, splitting the array into two non-empty subarrays such that: Left subarray contains indices [0, i]. Right subarray contains indices [i + 1, n - 1]. Return the number of partitions where the difference between the sum of the left and right subarrays is even.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn count_partitions(nums: Vec<i32>) -> i32 {
    let total: i32 = nums.iter().sum();
    if total % 2 == 0 { (nums.len() - 1) as i32 } else { 0 }
  }
}