Partition array into three parts with equal sum

Array Greedy

42.6% acceptance

Feb 25, 2026

1790

169

Given an array of integers arr, return true if we can partition the array into three non-empty parts with equal sums. Formally, we can partition the array if we can find indexes i + 1 < j with (arr[0] + arr[1] + ... + arr[i] == arr[i + 1] + arr[i + 2] + ... + arr[j - 1] == arr[j] + arr[j + 1] + ... + arr[arr.length - 1])

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn can_three_parts_equal_sum(arr: Vec<i32>) -> bool {
    let total: i32 = arr.iter().sum();
    if total % 3 != 0 { return false; }
    let target = total / 3;
    let mut parts = 0; let mut sum = 0;
    for &x in &arr {
      sum += x;
      if sum == target * (parts + 1) { parts += 1; }
    }
    parts >= 3
  }
}