LeetCode-in-Java

2255. Count Prefixes of a Given String

Easy

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. A substring is a contiguous sequence of characters within a string.

Example 1:

Input: words = [“a”,”b”,”c”,”ab”,”bc”,”abc”], s = “abc”

Output: 3

Explanation:

The strings in words which are a prefix of s = “abc” are:

“a”, “ab”, and “abc”.

Thus the number of strings in words which are a prefix of s is 3.

Example 2:

Input: words = [“a”,”a”], s = “aa”

Output: 2

Explanation:

Both of the strings are a prefix of s.

Note that the same string can occur multiple times in words, and it should be counted each time.

Constraints:

• 1 <= words.length <= 1000
• 1 <= words[i].length, s.length <= 10
• words[i] and s consist of lowercase English letters only.

Solution

public class Solution {
    public int countPrefixes(String[] words, String s) {
        int count = 0;
        for (String str : words) {
            if (s.indexOf(str) == 0) {
                ++count;
            }
        }
        return count;
    }
}

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