1961. Check If String Is a Prefix of Array

📝 Problem Details

• Title: 1961. Check If String Is a Prefix of Array
• Link: https://leetcode.com/problems/check-if-string-is-a-prefix-of-array/
• Difficulty: Easy
• Tags/Categories: Strings

💭What Were My Initial Thoughts?

- create a new string that concatenates the items in the input words vector
- check if the substr s exists in our new word 
	- this didnt take into account specifics for the question

🤔What Did I Struggle With?

- tried using .rfind() to check for a prefix exitsing but this didnt take into account the rule of it having to be a concatenation of the first k strings in words

💡 Explanation of Solution

1. initialise a new string newWord
2. iterate through s and insert each element into newWord
	- check if the newWord and s are equal, if they are return true
	- return false if the size of the newWord exceeds s OR if the substring of s with the same length of newWord are different

⌛ Complexity Analysis

Time Complexity: O(N + M) 
- n is the total length of words
- m is the length of s

Space Complexity: O(M) due to newWord string

💻 Implementation of Solution

    bool isPrefixString(string s, vector<string>& words) {
        string newWord;
 
        for (int i = 0; i < words.size(); ++i) {
            newWord += words[i];
            if (newWord == s) return true; // Exact match
            if (newWord.size() > s.size() || s.substr(0, newWord.size()) != newWord)
                return false; // Exceeded or mismatch
        }
        return false; // Not a prefix after processing all words
    }