1455. Check If a Word Occurs As a Prefix of Any Word in a Sentence

Description

Given a sentence that consists of some words separated by a single space, and a searchWord, check if searchWord is a prefix of any word in sentence.

Return the index of the word in sentence (1-indexed) where searchWord is a prefix of this word. If searchWord is a prefix of more than one word, return the index of the first word (minimum index). If there is no such word return -1.

A prefix of a string s is any leading contiguous substring of s.

 

Example 1:

Input: sentence = "i love eating burger", searchWord = "burg"
Output: 4
Explanation: "burg" is prefix of "burger" which is the 4th word in the sentence.

Example 2:

Input: sentence = "this problem is an easy problem", searchWord = "pro"
Output: 2
Explanation: "pro" is prefix of "problem" which is the 2nd and the 6th word in the sentence, but we return 2 as it's the minimal index.

Example 3:

Input: sentence = "i am tired", searchWord = "you"
Output: -1
Explanation: "you" is not a prefix of any word in the sentence.

 

Constraints:

• 1 <= sentence.length <= 100
• 1 <= searchWord.length <= 10
• sentence consists of lowercase English letters and spaces.
• searchWord consists of lowercase English letters.

 

Solutions

Solution: Brute Force

• Time complexity: O(L+W⋅min(s,l))
• Space complexity: O(L)
  • L: The total length of the string.
  • W: Number of words.
  • s: searchWord length.
  • l: average length of words.

 

JavaScript

/**
 * @param {string} sentence
 * @param {string} searchWord
 * @return {number}
 */
const isPrefixOfWord = function (sentence, searchWord) {
  const words = sentence.split(' ');
  const index = words.findIndex(word => word.startsWith(searchWord));

  return index === -1 ? -1 : index + 1;
};