Introduction

In this blog post, we will explore how to solve the LeetCode problem "796" 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 s and goal, return true if and only if s can become goal after some number of shifts on s. A shift on s consists of moving the leftmost character of s to the rightmost position. For example, if s = "abcde", then it will be "bcdea" after one shift. Example 1: Input: s = "abcde", goal = "cdeab" Output: true Example 2: Input: s = "abcde", goal = "abced" Output: false Constraints: 1 <= s.length, goal.length <= 100 s and goal consist of lowercase English letters.

Explanation

Here's a breakdown of the solution:

• String Concatenation and Substring Check: The core idea is to concatenate the original string s with itself. If goal is a rotation of s, then goal must exist as a substring within this concatenated string.

• Length Check: Before proceeding with the concatenation and substring check, we first confirm if the lengths of the two strings are equal. If they are not, it's impossible for one to be a rotation of the other, so we immediately return False.

• Optimization: Using the in operator in Python for substring checking is efficient for this problem's constraint of strings with lengths up to 100.

• Runtime and Storage Complexity:

  • Runtime: O(N), where N is the length of the strings s and goal.
  • Storage: O(N), due to the concatenated string s + s.

Code

    def rotateString(s: str, goal: str) -> bool:
    """
    Checks if string 'goal' can be obtained by rotating string 's'.
    """
    if len(s) != len(goal):
        return False

    concatenated_s = s + s
    return goal in concatenated_s