judge-route-circle.py

# Time:  O(n)
# Space: O(1)

# 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

class Solution(object):
    def judgeCircle(self, moves):
        """
        :type moves: str
        :rtype: bool
        """
        v, h = 0, 0
        for move in moves:
            if move == 'U':
                v += 1
            elif move == 'D':
                v -= 1
            elif move == 'R':
                h += 1
            elif move == 'L':
                h -= 1
        return v == 0 and h == 0