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:
Input: "UD" Output: true
Example 2:
Input: "LL" Output: false 思路：本题思路很简单，建立map容器，统计各个字符出现的次数，只要‘U'与’D';'R‘与’L'出现次数相等，就能回到原点，否则回不到原点。
代码：
class Solution { public: bool judgeCircle(string moves) { map<char,int> mp; for(int i=0;i<moves.size();i++) mp[moves[i]]++; if(mp['U']==mp['D']&&mp['L']==mp['R']) return true; else return false; } };
