LeetCode-in-Java

1961. Check If String Is a Prefix of Array

Easy

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.

Solution

public class Solution {
    public boolean isPrefixString(String s, String[] words) {
        StringBuilder sb = new StringBuilder();
        for (String word : words) {
            sb.append(word);
            if (sb.toString().equals(s)) {
                return true;
            }
        }
        return false;
    }
}

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