Q.

Implement strStr().

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.

A)

/**
 * @param {string} haystack
 * @param {string} needle
 * @return {number}
 */
var strStr = function(haystack, needle) {
  return haystack.indexOf(needle)
    
};

Runtime: 72 ms, faster than 89.45% of JavaScript online submissions for Implement strStr().
Memory Usage: 39.9 MB, less than 37.23% of JavaScript online submissions for Implement strStr().