Largest unique number

Array Hash Table Sorting

71.3% acceptance

Mar 31, 2026

356

Given an integer array nums, return the largest integer that only occurs once. If no integer occurs once, return -1.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn largest_unique_number(nums: Vec<i32>) -> i32 {
    let mut count = [0u16; 1001];
    for &n in &nums {
      count[n as usize] += 1;
    }
    for i in (0..=1000).rev() {
      if count[i] == 1 {
        return i as i32;
      }
    }
    -1
  }
}