Count number of distinct integers after reverse operations

Array Hash Table Math Counting

81.3% acceptance

Feb 25, 2026

742

You are given an array nums consisting of positive integers. You have to take each integer in the array, reverse its digits, and add it to the end of the array. You should apply this operation to the original integers in nums. * Return the number of distinct integers in the final array.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn count_distinct_integers(nums: Vec<i32>) -> i32 {
    use std::collections::HashSet;
    let mut set: HashSet<i32> = nums.iter().cloned().collect();
    for &n in &nums {
      let mut x = n;
      let mut rev = 0;
      while x > 0 {
        rev = rev * 10 + x % 10;
        x /= 10;
      }
      set.insert(rev);
    }
    set.len() as i32
  }
}