[ Leetcode ] 28. Implement strStr() - Java

Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

 

Clarification:

What should we return when needle is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().

 

 
 Example 1:

 Input: haystack = "hello", needle = "ll" 
 Output: 2
 

 
 Example 2:

 Input: haystack = "aaaaa", needle = "bba" 
 Output: -1
 

 
 Example 3:

 Input: haystack = "", needle = "" 
 Output: 0
 

 

Constraints:

• 0 <= haystack.length, needle.length <= 5 * 104
• haystack and needle consist of only lower-case English characters.

 

Solution

 
 class Solution {
    public int strStr(String haystack, String needle) {
        return haystack.indexOf(needle);
    }
 }