Check if n and its double exist

Array Hash Table Two Pointers Binary Search Sorting

41.7% acceptance

Feb 25, 2026

2515

257

Given an array arr of integers, check if there exist two indices i and j such that : i != j 0 <= i, j < arr.length arr[i] == 2 * arr[j]

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn check_if_exist(arr: Vec<i32>) -> bool {
    let mut set = std::collections::HashSet::new();
    for &x in &arr {
      if set.contains(&(x * 2)) || (x % 2 == 0 && set.contains(&(x / 2))) {
        return true;
      }
      set.insert(x);
    }
    false
  }
}