strStr.js

/*
https://leetcode.com/problems/implement-strstr/description/

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().

*/


const strStr = function(haystack, needle) {
    if (needle.length === 0) return 0;
    if (haystack.length < needle) return -1;
    for (let i = 0; i < haystack.length; i++) {
        if (haystack.substr(i, needle.length) === needle) {
            return i;
        }
    }
    return -1;
};