Count Prefixes of a Given String

Problem Description

You are given a string array words and a string s, where words[i] and s comprise only of lowercase English letters. Return the number of strings in words that are a prefix of s. A prefix of a string is a substring that occurs at the beginning of the string.

Key Insights

• A prefix is defined as a substring that must start at the beginning of the string s.
• Each word in words needs to be checked to see if it matches the start of s.
• Words can be repeated, and each occurrence should be counted.

Space and Time Complexity

Time Complexity: O(n * m) where n is the length of words and m is the maximum length of a string in words. Space Complexity: O(1) since we are using a constant amount of space for counting.

Solution

To solve the problem, we will iterate through each word in the words array and check if it is a prefix of the string s. We can use the string method startswith() to perform this check efficiently. We maintain a counter to track the number of prefixes found.

Code Solutions