题解 | #跳台阶#递推

    public int jumpFloor(int target) {
        //f(1) = 1
        //f(2) = 2
        //f(3) = 3 = f(1) + f(2)
        //f(4) = 5 = f(3) + f(2)
        //f(n) = f(n - 1) + f(n - 2)
        if(target == 1){
            return 1;
        }
        if(target == 2){
            return 2;
        }
        int a = 1;
        int b = 2;
        int res = 0;
        for(int i = 3;i<=target;i++){
            res = a + b;
            a = b;
            b = res;
        }
        return res;
    }
}