1041. 困于环中的机器人.cpp

class Solution {
public:
        bool isRobotBounded(string instructions) {
        int x = 0, y = 0, i = 0;
        vector<vector<int>> d = {{0, 1}, {1, 0}, {0, -1}, { -1, 0}};
        for (char & ins : instructions)
            if (ins == 'R')
                i = (i + 1) % 4;
            else if (ins == 'L')
                i = (i + 3) % 4;
            else
                x += d[i][0], y += d[i][1];
        return x == 0 && y == 0 || i > 0;
    }
};