657. Judge Route Circle【easy】

657. Judge Route Circle【easy】

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

解法一：

class Solution {
public:
    bool judgeCircle(string moves) {
        int h = 0;
        int w = 0;
        
        for (int i = 0; i < moves.length(); ++i) {
            if (moves[i] == 'U') {
                h++;
            } else if (moves[i] == 'D') {
                h--;
            } else if (moves[i] == 'R') {
                w++;
            } else if (moves[i] == 'L') {
                w--;
            }
        }
        
        return (h == 0 && w == 0);
    }
};

解法二：

class Solution {
public:
    bool judgeCircle(string moves) {
        unordered_map<char, int> c;
        for ( char m : moves )
            ++c[m];
        return c['L'] == c['R'] && c['U'] == c['D'];
    }
};

参考@zqfan 的代码。