Introduction

In this blog post, we will explore how to solve the LeetCode problem "2337" 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

You are given two strings start and target, both of length n. Each string consists only of the characters 'L', 'R', and '' where: The characters 'L' and 'R' represent pieces, where a piece 'L' can move to the left only if there is a blank space directly to its left, and a piece 'R' can move to the right only if there is a blank space directly to its right. The character '' represents a blank space that can be occupied by any of the 'L' or 'R' pieces. Return true if it is possible to obtain the string target by moving the pieces of the string start any number of times. Otherwise, return false. Example 1: Input: start = "LRR", target = "L__RR" Output: true Explanation: We can obtain the string target from start by doing the following moves: - Move the first piece one step to the left, start becomes equal to "L_RR_". - Move the last piece one step to the right, start becomes equal to "LRR". - Move the second piece three steps to the right, start becomes equal to "L__RR". Since it is possible to get the string target from start, we return true. Example 2: Input: start = "RL", target = "__LR" Output: false Explanation: The 'R' piece in the string start can move one step to the right to obtain "RL". After that, no pieces can move anymore, so it is impossible to obtain the string target from start. Example 3: Input: start = "R", target = "R" Output: false Explanation: The piece in the string start can move only to the right, so it is impossible to obtain the string target from start. Constraints: n == start.length == target.length 1 <= n <= 105 start and target consist of the characters 'L', 'R', and '_'.

Explanation

Here's a breakdown of the solution:

• Ignore Blanks: The core idea is that blank spaces ('_') are just placeholders and don't affect the relative order of 'L' and 'R' pieces. We only care about whether the 'L's and 'R's are in the correct relative positions in both strings.
• Validate 'L' Movements: For 'L' pieces, an 'L' in the start string can only move to the left to reach its position in the target string. Therefore, the index of 'L' in start must be greater than or equal to its index in target.

• Validate 'R' Movements: Similarly, for 'R' pieces, an 'R' in the start string can only move to the right. The index of 'R' in start must be less than or equal to its index in target.

• Runtime Complexity: O(n), where n is the length of the strings.

• Storage Complexity: O(1)

Code

    def canTransform(start: str, target: str) -> bool:
    """
    Determines if it is possible to obtain the string target from start by moving
    the 'L' and 'R' pieces.

    Args:
        start: The starting string.
        target: The target string.

    Returns:
        True if it is possible to transform start to target, False otherwise.
    """

    n = len(start)
    i = 0
    j = 0

    while i < n and j < n:
        while i < n and start[i] == '_':
            i += 1
        while j < n and target[j] == '_':
            j += 1

        if i < n and j < n:
            if start[i] != target[j]:
                return False

            if start[i] == 'L':
                if i < j:
                    return False
            elif start[i] == 'R':
                if i > j:
                    return False

            i += 1
            j += 1

    while i < n and start[i] == '_':
        i += 1
    while j < n and target[j] == '_':
        j += 1

    return i == n and j == n