Judge Route Circle --判断圆路线

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：  
　　　　1.这是一个模拟横纵坐标移动的问题，向左移动x--，向右x++，向上y++，向下y--，最后判断 x == 0 && y == 0即可。
　　　　2.直接判断'L','R','U','D'出现的次数是否相等
实现代码：

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;  
    }
};