Leetcode 28

Implement strStr()

문제 출처

문제

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.

나의 코드

/**
 * @param {string} haystack
 * @param {string} needle
 * @return {number}
 */
const strStr = function (haystack, needle) {
  if (haystack === needle || needle.length === 0) return 0;

  const lengthOfSearchBundle = needle.length;

  for (let i = 0; i <= haystack.length - lengthOfSearchBundle; i++) {
    const bundle = haystack.slice(i, i + lengthOfSearchBundle);
    if (bundle === needle) return i;
  }
  return -1;
};

참고 코드

var strStr = function (haystack, needle) {
  if (needle.length == 0) return 0;
  for (let i = 0; i < haystack.length; i++) {
    let k = i,
      j = 0;
    while (haystack[k] == needle[j] && j < needle.length) {
      k++, j++;
    }
    if (j == needle.length) return i;
  }
  return -1; // couldn't find needle in haystack
  // Time Complexity: O(m*n)
  // Space Complexity: O(1)
};

배운점