跳台阶_08

public int jumpFloor(int target) {
        if (target==1){
            return 1;
        }
        if (target==2){
            return 2;
        }
        //可能从前一级和前两集跳上来的
        return jumpFloor(target-1)+jumpFloor(target-2);
    }

public int jumpFloor(int target) {
        if (target==0||target==1){
            return target;
        }
        int sum=1;
        int one =1;
        for (int i = 2; i <=target ; i++) {
            sum=sum+one;
            one=sum-one;
        }
        return sum;
    }