Longest balanced subarray i

Array Hash Table Divide and Conquer Segment Tree Prefix Sum

65.7% acceptance

Feb 24, 2026

479

You are given an integer array nums. A subarray is called balanced if the number of distinct even numbers in the subarray is equal to the number of distinct odd numbers. Return the length of the longest balanced subarray.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn longest_balanced(nums: Vec<i32>) -> i32 {
    let n = nums.len();
    let mut best = 0;
    for i in 0..n {
      let mut evens = std::collections::HashSet::new();
      let mut odds = std::collections::HashSet::new();
      for j in i..n {
        if nums[j] % 2 == 0 { evens.insert(nums[j]); } else { odds.insert(nums[j]); }
        if evens.len() == odds.len() {
          best = best.max((j - i + 1) as i32);
        }
      }
    }
    best
  }
}