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
用x,y代表横纵坐标上面的移动，然后根据移动方向加或者减1.

 1 class Solution {
 2     public boolean judgeCircle(String moves) {
 3         int x = 0, y = 0;
 4         for (char move: moves.toCharArray()) {
 5             if (move == 'U') y--;
 6             else if (move == 'D') y++;
 7             else if (move == 'L') x--;
 8             else if (move == 'R') x++;
 9         }
10         return x == 0 && y == 0;
11     }
12 }