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

Example 1:

Input: "UD"
Output: true

Example 2:

Input: "LL"
Output: false

思路：  
　　　　1.這是一個模擬橫縱坐標移動的問題，向左移動x--，向右x++，向上y++，向下y--，最後判斷 x == 0 && y == 0即可。
　　　　2.直接判斷‘L‘,‘R‘,‘U‘,‘D‘出現的次數是否相等
實現代碼：

class Solution {
 
public:
    bool judgeCircle(string moves) {
        int x=0,y=0;
          for (int i = 0; i < moves.length(); i++){  
            if (moves[i] == ‘L‘) x--;  
            else if (moves[i] == ‘R‘) x++;  
            else if (moves[i] == ‘U‘) y++;  
            else y--;  
        }  
        return
 
 x == 0 && y == 0;  
    }
};

Judge Route Circle --判斷圓路線