[LeetCode]657. Judge Route Circle

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题目

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:

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Input: "UD"
Output: true

Example 2:

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Input: "LL"
Output: false

难度

Easy

方法

对每个方向计数，如果L出现的次数==R出现的次数，并且U出现的次数==D出现的次数，则robot会回到初始位置，返回True；否则返回False

python代码

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class Solution(object):
    def judgeCircle(self, moves):
        """
        :type moves: str
        :rtype: bool
        """
        counter = {}
        for c in moves:
            counter[c] = counter.get(c, 0) + 1

        return counter.get("L") == counter.get("R") and counter.get("U") == counter.get("D")

assert Solution().judgeCircle("UD") == True
assert Solution().judgeCircle("LL") == False