Formatted question description: https://leetcode.ca/all/1903.html

# 1903. Largest Odd Number in String

## Level

Easy

## 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 existsA **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 <= 10^5`

`num`

only consists of digits and does not contain any leading zeros.

## Solution

Any number that ends with an odd digit is an odd number. If a digit in `num`

is an odd number, then the substring from index 0 to the current digit is ghe largest odd number that ends with the digit. Therefore, find the rightmost odd digit in `nums`

, and return the substring from index 0 to the rightmost odd digit.

```
class Solution {
public String largestOddNumber(String num) {
for (int i = num.length() - 1; i >= 0; i--) {
char c = num.charAt(i);
int digit = c - '0';
if (digit % 2 != 0)
return num.substring(0, i + 1);
}
return "";
}
}
```