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： 用一个pair变量(x,y)来保存坐标，遍历字符串中的每一个字符，如果为R，x加1；如果为L，x减1；如果为U，y加1；如果为D，y减1。如果最终坐标为(0,0)，那么就代表在回到了原点，返回true。

代码：

class Solution {public:    bool judgeCircle(string moves) {        int len = moves.length();        pair<int, int> res(0, 0);//用pair保存坐标位置        for (int i = 0; i < len; ++i){            switch (moves[i]){//遍历字符串，按直接坐标分别对每一个字符进行判断            case 'R':                res.first += 1; break;            case 'L':                res.first -= 1; break;            case 'U':                res.second += 1; break;            case 'D':                res.second -= 1; break;            default:break;            }        }        return !(res.first+res.second);//如果最终坐标为(0,0)就为true    }};

结果： 19ms