028_Implement_strStr().java

// 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 res = -1;
        for(int i = 0; i <= haystack.length()-needle.length(); i ++){
            if(haystack.substring(i, i+needle.length()).equals(needle)){
                res = i;
                break;
            }
        }
        return res;
    }
}