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

Solution

(1) Java

(2) Python

class Solution:
    def judgeCircle(self, moves):
        """
        :type moves: str
        :rtype: bool
        """
        if not moves:
            return True
        steps = [0,0]
        for m in moves:
            if m == 'U':
                steps[0] += 1
            elif m == 'D':
                steps[0] += -1
            elif m == 'L':
                steps[1] += -1
            else:
                steps[1] += 1
        return steps[0] == 0 and steps[1] == 0

(3) Scala