nitially, 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 tothe 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
原文：https://www.cnblogs.com/MarkLeeBYR/p/10688254.html