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

Solution 1

bool judgeCircle(string moves) {
    int x = 0;
    int y = 0;

    for (auto move: moves) {
        switch (move) {
            case 'U':
                y += 1;
                break;
            case 'D':
                y -= 1;
                break;
            case 'L':
                x -= 1;
                break;
            case 'R':
                x += 1;
            default:
                continue;
        }
    }

    return x == 0 && y == 0;
}

Solution: Using Pair

bool judgeCircle(string moves) {
    pair<int, int> pos;
    unordered_map<char, pair<int, int>> m;
    m['U'] = make_pair(0, 1);
    m['D'] = make_pair(0, -1);
    m['L'] = make_pair(-1, 0);
    m['R'] = make_pair(1, 0);

    for (auto move: moves) {
        pos.first += m[move].first;
        pos.second += m[move].second;
    }

    return pos == make_pair(0, 0);
}