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# 1903. Largest Odd Number in String

<https://leetcode.com/problems/largest-odd-number-in-string>

## Description

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.

## ac

```java
```