5.leetCode：657. Judge Route Circle

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：只要判断往上走的步数和往下走的步数相同，且往左走的步数和往右走的步数相同，则回到了原点。

代码：

class Solution {    public boolean judgeCircle(String moves) {        char[] c = moves.toCharArray();        int x = 0, y=0;        for(int i=0;i<c.length;i++){            if(c[i]=='L')                x++;            else if(c[i] == 'R')                x--;            else if(c[i] == 'U')                y++;            else                y--;        }        return (x==0 && y==0);    }}