# Solving Leetcode Interviews in Seconds with AI: Check If String Is a Prefix of Array


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "1961" 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
	> Given a string s and an array of strings words, determine whether s is a prefix string of words. A string s is a prefix string of words if s can be made by concatenating the first k strings in words for some positive k no larger than words.length. Return true if s is a prefix string of words, or false otherwise.   Example 1:  Input: s = "iloveleetcode", words = ["i","love","leetcode","apples"] Output: true Explanation: s can be made by concatenating "i", "love", and "leetcode" together.  Example 2:  Input: s = "iloveleetcode", words = ["apples","i","love","leetcode"] Output: false Explanation: It is impossible to make s using a prefix of arr.   Constraints:  1 <= words.length <= 100 1 <= words[i].length <= 20 1 <= s.length <= 1000 words[i] and s consist of only lowercase English letters.  

	# Explanation
	Here's a breakdown of the solution:

*   **Iterative Concatenation:** The solution iterates through the `words` array, concatenating the strings one by one.
*   **Prefix Check:** After each concatenation, it checks if the concatenated string equals `s`. If it does, it means `s` is a prefix string.
*   **Early Exit:** If the concatenated string becomes longer than `s`, it's impossible for `s` to be a prefix, so the function immediately returns `False`.

*   **Runtime Complexity:** O(n*m) where n is the number of words and m is the average length of the words. **Storage Complexity:** O(1) (excluding the input strings).

	
	# Code
	```python
	def isPrefixString(s: str, words: list[str]) -> bool:
    """
    Given a string s and an array of strings words, determine whether s is a prefix string of words.
    A string s is a prefix string of words if s can be made by concatenating the first k strings in words
    for some positive k no larger than words.length.
    Return true if s is a prefix string of words, or false otherwise.

    Example 1:
    Input: s = "iloveleetcode", words = ["i","love","leetcode","apples"]
    Output: true
    Explanation: s can be made by concatenating "i", "love", and "leetcode" together.

    Example 2:
    Input: s = "iloveleetcode", words = ["apples","i","love","leetcode"]
    Output: false
    Explanation: It is impossible to make s using a prefix of arr.

    Constraints:
    1 <= words.length <= 100
    1 <= words[i].length <= 20
    1 <= s.length <= 1000
    words[i] and s consist of only lowercase English letters.
    """
    prefix = ""
    for word in words:
        prefix += word
        if prefix == s:
            return True
        if len(prefix) > len(s):
            return False
    return False
	```