leetcode874

这道题直接按照题意来解，建立坐标系和移动方案，思路是比较简单的。只是需要注意需要使用set来判断是否遇到障碍，否则会超时。

int robotSim(vector<int>& commands, vector<vector<int>>& obstacles) {

    int N = commands.size();
    int M = obstacles.size();

    //向上 Wx=0,Wy=1
    //向左 Wx=-1,Wy=0
    //向下 Wx=0,Wy=-1
    //向右 Wx=1,Wy=0

    set<pair<int, int>> st;
    for (auto &obs : obstacles)
    {
        st.insert(make_pair(obs[0], obs[1]));
    }

    int Wx = 0;
    int Wy = 1;

    int Px = 0;
    int Py = 0;
    int maxdistance = 0;

    for (int i = 0; i < N; i++)
    {
        int cmd = commands[i];//当前指令        
        if (cmd == -2)//左转
        {
            if (Wx == 0 && Wy == 1)//上-->左
            {
                Wx = -1;
                Wy = 0;
            }
            else if (Wx == -1 && Wy == 0)//左-->下
            {
                Wx = 0;
                Wy = -1;
            }
            else if (Wx == 0 && Wy == -1)//下-->右
            {
                Wx = 1;
                Wy = 0;
            }
            else if (Wx == 1 && Wy == 0)//右-->上
            {
                Wx = 0;
                Wy = 1;
            }
        }
        else if (cmd == -1)//右转
        {
            if (Wx == 0 && Wy == 1)//上-->右
            {
                Wx = 1;
                Wy = 0;
            }
            else if (Wx == -1 && Wy == 0)//左-->上
            {
                Wx = 0;
                Wy = 1;
            }
            else if (Wx == 0 && Wy == -1)//下-->左
            {
                Wx = -1;
                Wy = 0;
            }
            else if (Wx == 1 && Wy == 0)//右-->下
            {
                Wx = 0;
                Wy = -1;
            }
        }
        else//移动 1<=x<=9
        {
            //此次移动之前的起点位置为Px和Py
            int Tmpx = Px;
            int Tmpy = Py;
            while (cmd > 0)
            {
                //以(Wx,Wy)为步进，移动一次
                Tmpx += Wx;
                Tmpy += Wy;

                if (st.find(make_pair(Tmpx, Tmpy)) != st.end())
                {
                    Tmpx -= Wx;
                    Tmpy -= Wy;
                    cmd = 0;
                }
                cmd--;
            }
            int distance = Tmpx*Tmpx + Tmpy*Tmpy;
            if (maxdistance < distance)
            {
                maxdistance = distance;
            }
            Px = Tmpx;
            Py = Tmpy;
        }
    }

    return maxdistance;
}