Robot Return to Origin: LeetCode Java Solution

This Java solution for LeetCode 657, Robot Return to Origin, checks whether the robot finishes at (0, 0) by balancing vertical and horizontal moves.

Problem Statement

There is a robot starting at 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.

The move sequence is represented by a string, and the character moves[i] represents its ith move. Valid moves are R (right), L (left), U (up), and D (down). If the robot returns to the origin after it finishes all of its moves, return true. Otherwise, return false.

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.

Reverse Integer in Java: Simple Explanation and Code

Explanation

Example 1:

Input:

moves = “UD”

Output:

true

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.

Constraints

• 1 <= moves.length <= 2 * 104
• moves only contains the characters 'U', 'D', 'L' and 'R'.

Test Cases

Test Case 1

Input:

moves = “LL”

Output:

false

Explanation

The robot moves left twice. It ends up with two “moves” to the left of the origin. We return false because it is not at the origin at the end of its moves.

Test Case 2

Input:

moves = “RRDD”

Output:

false

Test Case 3

Input:

moves = “LDRRLRUULR”

Output:

false

Solution

Leetcode Link

https://leetcode.com/problems/robot-return-to-origin/