Introduction

In this blog post, we will explore how to solve the LeetCode problem "28" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1: Input: haystack = "sadbutsad", needle = "sad" Output: 0 Explanation: "sad" occurs at index 0 and 6. The first occurrence is at index 0, so we return 0. Example 2: Input: haystack = "leetcode", needle = "leeto" Output: -1 Explanation: "leeto" did not occur in "leetcode", so we return -1. Constraints: 1 <= haystack.length, needle.length <= 104 haystack and needle consist of only lowercase English characters.

Explanation

Here's a breakdown of the approach and the Python code:

• High-Level Approach:

  • Iterate through the haystack string, checking for potential starting positions of the needle.
  • At each potential starting position, compare the substring of haystack with the needle.
  • Return the index of the first match found, otherwise return -1 if no match is found after iterating through the haystack string.

• Complexity Analysis:

  • Runtime Complexity: O(m*n), where n is the length of the haystack and m is the length of the needle.
  • Storage Complexity: O(1). We use constant extra space.

Code

    def strStr(haystack: str, needle: str) -> int:
    """
    Finds the index of the first occurrence of needle in haystack.

    Args:
        haystack: The string to search within.
        needle: The string to search for.

    Returns:
        The index of the first occurrence of needle in haystack, or -1 if not found.
    """

    n = len(haystack)
    m = len(needle)

    if m == 0:
        return 0

    for i in range(n - m + 1):
        if haystack[i:i+m] == needle:
            return i

    return -1