Check If String Is a Prefix of Array

Problem Description

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.

Key Insights

• A prefix string is formed by concatenating the first k elements of an array.
• We need to check if the concatenated string matches the given string s.
• We can iterate through the words array and build the prefix incrementally until we either match s or exceed its length.

Space and Time Complexity

Time Complexity: O(n), where n is the number of strings in the words array. Space Complexity: O(1), as we are using a constant amount of additional space.

Solution

The solution uses a simple iterative approach to concatenate strings from the array until the concatenated string either matches the target string s or exceeds its length. The algorithm keeps a running total of the concatenated string as it progresses through the array.

1. Initialize an empty string to build the prefix.
2. Iterate through the array of words, appending each word to the prefix.
3. After each append, check if the prefix matches the string s.
4. If a match is found, return true. If the length of the prefix exceeds that of s, return false at the end.

Code Solutions