Introduction

In this blog post, we will explore how to solve the LeetCode problem "657" 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

There is a robot starting at the position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it completes its moves. You are given a string moves that represents the move sequence of the robot where moves[i] represents its ith move. Valid moves are 'R' (right), 'L' (left), 'U' (up), and 'D' (down). Return true if the robot returns to the origin after it finishes all of its moves, or false otherwise. Note: The way that the robot is "facing" is irrelevant. 'R' will always make the robot move to the right once, 'L' will always make it move left, etc. Also, assume that the magnitude of the robot's movement is the same for each move. Example 1: Input: moves = "UD" Output: true Explanation: The robot moves up once, and then down once. All moves have the same magnitude, so it ended up at the origin where it started. Therefore, we return true. Example 2: Input: moves = "LL" Output: false Explanation: The robot moves left twice. It ends up two "moves" to the left of the origin. We return false because it is not at the origin at the end of its moves. Constraints: 1 <= moves.length <= 2 * 104 moves only contains the characters 'U', 'D', 'L' and 'R'.

Explanation

• Track Coordinates: Maintain the robot's x and y coordinates.
  • Update Coordinates: Iterate through the move sequence, updating the x and y coordinates based on each move ('R', 'L', 'U', 'D').
  • Check Origin: After processing all moves, check if the final x and y coordinates are both 0.

• Runtime Complexity: O(n), where n is the length of the moves string. Storage Complexity: O(1).

Code

    def judgeCircle(moves: str) -> bool:
    """
    Determines if a robot returns to the origin after a sequence of moves.

    Args:
        moves: A string representing the move sequence.

    Returns:
        True if the robot returns to the origin, False otherwise.
    """
    x = 0
    y = 0
    for move in moves:
        if move == 'R':
            x += 1
        elif move == 'L':
            x -= 1
        elif move == 'U':
            y += 1
        elif move == 'D':
            y -= 1
    return x == 0 and y == 0