# Solving Leetcode Interviews in Seconds with AI: Find Smallest Letter Greater Than Target


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "744" 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 an array of characters letters that is sorted in non-decreasing order, and a character target. There are at least two different characters in letters. Return the smallest character in letters that is lexicographically greater than target. If such a character does not exist, return the first character in letters.   Example 1:  Input: letters = ["c","f","j"], target = "a" Output: "c" Explanation: The smallest character that is lexicographically greater than 'a' in letters is 'c'.  Example 2:  Input: letters = ["c","f","j"], target = "c" Output: "f" Explanation: The smallest character that is lexicographically greater than 'c' in letters is 'f'.  Example 3:  Input: letters = ["x","x","y","y"], target = "z" Output: "x" Explanation: There are no characters in letters that is lexicographically greater than 'z' so we return letters[0].    Constraints:  2 <= letters.length <= 104 letters[i] is a lowercase English letter. letters is sorted in non-decreasing order. letters contains at least two different characters. target is a lowercase English letter.  

	# Explanation
	Here's the breakdown of the solution:

*   **Binary Search:** Leverage the sorted nature of the `letters` array to efficiently find the target's successor using binary search.
*   **Wrap-around:** Handle the case where the target is larger than all characters in `letters` by returning the first element.

*   **Time Complexity:** O(log n), where n is the length of the `letters` array. **Space Complexity:** O(1).

	
	# Code
	```python
	def nextGreatestLetter(letters, target):
    """
    Finds the smallest character in letters that is lexicographically greater than target.

    Args:
        letters: A sorted array of characters.
        target: A character.

    Returns:
        The smallest character in letters that is lexicographically greater than target.
        If such a character does not exist, return the first character in letters.
    """
    left = 0
    right = len(letters) - 1

    while left <= right:
        mid = left + (right - left) // 2
        if letters[mid] > target:
            right = mid - 1
        else:
            left = mid + 1

    return letters[left % len(letters)]
	```