Largest odd number in string

Math String Greedy

67.0% acceptance

Feb 25, 2026

2562

148

You are given a string num, representing a large integer. Return the largest-valued odd integer (as a string) that is a non-empty substring of num, or an empty string "" if no odd integer exists. A substring is a contiguous sequence of characters within a string.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn largest_odd_number(num: String) -> String {
    for (i, b) in num.bytes().enumerate().rev() {
      if (b - b'0') % 2 == 1 {
        return num[..=i].to_string();
      }
    }
    String::new()
  }
}