Minimum sum of four digit number after splitting digits

Math Greedy Sorting

86.2% acceptance

Feb 25, 2026

1505

148

You are given a positive integer num consisting of exactly four digits. Split num into two new integers new1 and new2 using the digits found in num (all digits must be used). Return the minimum possible sum of new1 and new2.

Solution

Rust

Time O(n log n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn minimum_sum(num: i32) -> i32 {
    let mut digits = [
      num / 1000,
      (num / 100) % 10,
      (num / 10) % 10,
      num % 10,
    ];
    digits.sort_unstable();
    // Assign smallest two digits as tens digits, largest two as units digits
    // new1 = d[0]*10 + d[2], new2 = d[1]*10 + d[3]
    // Sum = 10*(d[0]+d[1]) + (d[2]+d[3])
    digits[0] * 10 + digits[1] * 10 + digits[2] + digits[3]
  }
}