0028. Implement strStr().js

// 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().



/**
 * @param {string} haystack
 * @param {string} needle
 * @return {number}
 */
const strStr = (haystack, needle) => {
  if (needle == null || needle === '') {
    return 0
  }
  for (let i = 0; i < haystack.length - needle.length + 1; i++) {
    if (haystack.substr(i, needle.length) === needle) {
      return i
    }
  }
  return -1
}
// Runtime: 60 ms, faster than 47.22% of JavaScript online submissions for Implement strStr().
// Memory Usage: 33.8 MB, less than 85.71% of JavaScript online submissions for Implement strStr().