657. Judge Route Circle

Posted 2020-10-06 Yancea --- TO BE A DOER !

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


思路：Robot从(0,0)通过上下左右移动，最终会回到初始位置（move:str）。
　　　1.判断U-D, L-R是否成对出现，即上下或者左右移动次数相同；
　　　2.横纵坐标移动问题，保证xy最后回到原点，即x=0，y=0；

# 判断U-D，L-R是否成对出现

class Solution():
    def judgeCircle(self, moves):
        """
        :type moves: str
        :rtype: bool
        """
        return moves.count(‘L‘) == moves.count(‘R‘) and                 moves.count(‘U‘) == moves.count(‘D‘) 

# 横纵坐标移动问题
class Solution():
    def judgeCircle(self, moves):
        """
        :type moves: str
        :rtype: bool
        """
        x = 0
        y = 0
        for i in moves:
            if i == ‘L‘:
                x -= 1
            elif i == ‘R‘:
                x += 1
            elif i == ‘U‘:
                y += 1
            else:
                y -= 1
        return x == 0 and y == 0