Leetcode 657. Judge Route Circle

Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot makes a circle, which means it moves back to the original place.

The move sequence is represented by a string. And each move is represent by a character. The valid robot moves are R (Right), L(Left), U (Up) and D (down). The output should be true or false representing whether the robot makes a circle.

Example 1:

Input: "UD"
Output: true

Example 2:

Input: "LL"
Output: false

Code (Java):

class Solution {
    public boolean judgeCircle(String moves) {
        if (moves == null || moves.length() == 0) {
            return true;
        }
        
        int x = 0;
        int y = 0;
        
        for (int i = 0; i < moves.length(); i++) {
            char move = moves.charAt(i);
            switch (move) {
                case 'U':
                    y++;
                    break;
                case 'D':
                    y--;
                    break;
                case 'L':
                    x--;
                    break;
                case 'R':
                    x++;
                    break;
            }
        }
        
        return x == 0 && y == 0;
    }
}