1041

class Solution {
public:
    bool isRobotBounded(string ins) {
        // north=0, east=1, south=2, west=3
        int dir[4][2] = {{0,1},{1,0},{0,-1},{-1,0}};
        int x=0, y=0;
        int idx=0;
        for(char ch: ins){
            if(ch == 'L'){
                idx = (idx+3)%4;
            }
            else if( ch == 'R'){
                idx = (idx+1)%4;
            }
            else{
                x += dir[idx][0];
                y += dir[idx][1];
            }
        }
        return (x==0 && y==0) || (idx != 0);
    }
};