Judge Route Circle

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

 

这道题是判断一个路径是否绕圈，也就是U和D，L和R的个数要求相等。可以使用两个计数器，如果是U，则cnt1自增1；如果是D，cnt1自减1。同理，如果是L，则cnt1自增1；如果是R，cnt1自减1。最后只要看cnt1和cnt2是否同时为0。

class Solution {
public:
    bool judgeCircle(string moves) {
        int cnt1 = 0, cnt2 = 0;
        for (char move : moves) {
            if (move == 'U') ++cnt1;
            else if (move == 'D') --cnt1;
            else if (move == 'L') ++cnt2;
            else if (move == 'R') --cnt2;
        }
        return cnt1 == 0 && cnt2 == 0;
    }
};