Formatted question description: https://leetcode.ca/all/1455.html

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

Given a sentence that consists of some words separated by a single space, and a searchWord.

You have to check if searchWord is a prefix of any word in sentence.

Return the index of the word in sentence where searchWord is a prefix of this word (1-indexed).

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.

Example 4:

Input: sentence = "i use triple pillow", searchWord = "pill"
Output: 4

Example 5:

Input: sentence = "hello from the other side", searchWord = "they"
Output: -1

 

Constraints:

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

Related Topics:
String

Solution 1.

Keep extracting word as word out of s and check if w is a prefix of word.

// OJ: https://leetcode.com/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence/

// Time: O(S)
// Space: O(S)
class Solution {
public:
    int isPrefixOfWord(string s, string w) {
        istringstream ss(s);
        string word;
        for (int i = 1; ss >> word; ++i) {
            if (word.size() >= w.size() && word.substr(0, w.size()) == w) return i;
        }
        return -1;
    }
};

Solution 2.

Some other variations that just require constant extra space for string comparison.

// OJ: https://leetcode.com/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence/

// Time: O(S)
// Space: O(S)
class Solution {
public:
    int isPrefixOfWord(string s, string w) {
        istringstream ss(s);
        string word;
        for (int i = 1; ss >> word; ++i) {
            if (word.size() >= w.size() && mismatch(w.begin(), w.end(), word.begin()).first == w.end()) return i;
        }
        return -1;
    }
};
// OJ: https://leetcode.com/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence/

// Time: O(S)
// Space: O(S)
class Solution {
public:
    int isPrefixOfWord(string s, string w) {
        istringstream ss(s);
        string word;
        for (int i = 1; ss >> word; ++i) {
            string_view wv(word);
            if (word.size() >= w.size() && wv.substr(0, w.size()) == w) return i;
        }
        return -1;
    }
};

Java

class Solution {
    public int isPrefixOfWord(String sentence, String searchWord) {
        if (sentence == null || searchWord == null || searchWord.length() == 0 || sentence.length() < searchWord.length())
            return -1;
        String[] array = sentence.split(" ");
        int length = array.length;
        for (int i = 0; i < length; i++) {
            String word = array[i];
            if (word.indexOf(searchWord) == 0)
                return i + 1;
        }
        return -1;
    }
}

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