README_EN.md

1961. Check If String Is a Prefix of Array

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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.

 

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.

Solutions

Python3

class Solution:
    def isPrefixString(self, s: str, words: List[str]) -> bool:
        t = 0
        for i, w in enumerate(words):
            t += len(w)
            if len(s) == t:
                return ''.join(words[: i + 1]) == s
        return False

Java

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

C++

class Solution {
public:
    bool isPrefixString(string s, vector<string>& words) {
        string t = "";
        for (string& w : words) {
            t += w;
            if (t.size() == s.size()) return t == s;
        }
        return false;
    }
};

Go

func isPrefixString(s string, words []string) bool {
	t := ""
	for _, w := range words {
		t += w
		if t == s {
			return true
		}
	}
	return false
}

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