public class Solution
extends Object
1903 - Largest Odd Number in String\.
Easy
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.