# Solving Leetcode Interviews in Seconds with AI: Largest Odd Number in String


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "1903" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like [Chatmagic](https://www.chatmagic.app), we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

	# Problem Statement
	> 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.  

	# Explanation
	Here's the breakdown of the solution:

*   **Right-to-Left Scan:** Iterate through the string `num` from right to left. This allows us to find the largest odd number substring quickly.
*   **Odd Digit Found:** If an odd digit is encountered, the substring from the beginning of `num` up to and including that odd digit is the largest odd substring.
*   **No Odd Digit:** If the loop completes without finding an odd digit, it means no odd substring exists, so return an empty string.

*   **Runtime Complexity:** O(n), where n is the length of the input string `num`.
*   **Storage Complexity:** O(1) - constant extra space.

	
	# Code
	```python
	def largestOddNumber(num: str) -> str:
    """
    Finds the largest-valued odd integer that is a non-empty substring of num.

    Args:
        num: A string representing a large integer.

    Returns:
        The largest odd integer substring, or an empty string if none exists.
    """
    for i in range(len(num) - 1, -1, -1):
        if int(num[i]) % 2 != 0:
            return num[:i + 1]
    return ""
	```