Add to array form of integer

Array Math

45.4% acceptance

Feb 25, 2026

3679

316

The array-form of an integer num is an array representing its digits in left to right order. For example, for num = 1321, the array form is [1,3,2,1]. Given num, the array-form of an integer, and an integer k, return the array-form of the integer num + k.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn add_to_array_form(num: Vec<i32>, k: i32) -> Vec<i32> {
    let mut carry = k;
    let mut res: Vec<i32> = Vec::new();
    let mut i = num.len() as i32 - 1;
    while i >= 0 || carry > 0 {
      if i >= 0 { carry += num[i as usize]; i -= 1; }
      res.push(carry % 10);
      carry /= 10;
    }
    res.reverse();
    res
  }
}