README.md

1903. Largest Odd Number in String

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.

Example 1:

Input: num = "52"
Output: "5"
Explanation: The only non-empty substrings are "5", "2", and "52". "5" is the only odd number.

Example 2:

Input: num = "4206"
Output: ""
Explanation: There are no odd numbers in "4206".

Example 3:

Input: num = "35427"
Output: "35427"
Explanation: "35427" is already an odd number.

Constraints:

• 1 <= num.length <= 105
• num only consists of digits and does not contain any leading zeros.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn largest_odd_number(num: String) -> String {
        let mut num = num.into_bytes();

        while *num.last().unwrap_or(&1) % 2 == 0 {
            num.pop();
        }

        String::from_utf8(num).unwrap()
    }
}