difficult：easy #657
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：

#include<string>
#include<map>
bool judgeCircle(std::string moves) {
    std::map<char, int> action = { {'R',0},{'L',0},{'U',0},{'D',0} };
    for (int i = 0; i < moves.size(); i++) {
        action[moves[i]]++;
    }
    return action['R'] == action['L'] && action['U'] == action['D'];
}

解法二：

#include<string>
#include<map>
bool judgeCircle(std::string moves) {
    int x = 0, y = 0;
    for (char move:moves) {
        if (move == 'U') y--;
        else if (move == 'D') y++;
        else if (move == 'R') x--;
        else if (move == 'L') x++;
    }
    return x == 0 && y == 0;
}

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