leetcode 28. Implement strStr()

Seawolf

Implement strStr().

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

Example 1:

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

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

class Solution {
    public int strStr(String haystack, String needle) {
        
        int l1 = haystack.length();
        
        int l2 = needle.length();
        
        for(int i = 0; i< l1 - l2 + 1; i ++){
            
            // System.out.println(haystack.substring(i,i+l2));
            
            if(haystack.substring(i,i+l2).equals(needle)){
                
                return i;
            }
        }
        
        return -1;
        
    }
}