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;
}
}