657. Judge Route Circle

题目描述：

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

解题思路：
统计输入字符串中字符U和D的个数是否一样，L和R个数是否一样，若都一样，则返回到起点。

代码：

class Solution {
public:
    bool judgeCircle(string moves) {
        
        int u = 0;
        int d = 0;
        int l = 0;
        int r = 0;
        u = std::count(moves.begin(), moves.end(), 'U');
        d = std::count(moves.begin(), moves.end(), 'D');
        l = std::count(moves.begin(), moves.end(), 'L');
        r = std::count(moves.begin(), moves.end(), 'R');
        return (u == d) && (l == r);   
    }
};