跳台阶

public class jumpFloor {
    public int jumpFloor(int num){
        if(num < 0){
            return 0;
        }else if(num == 1){
            return 1;
        }else if ( num == 2){
            return 2;
        }else{
            return jumpFloor(num - 1) + jumpFloor(num - 2);
        }
    }
}