动态规划

    public int JumpFloor(int target) {

        if (target <= 2){
            return target;
        }

        int pre_1 = 2;
        int pre_2 = 1;
        int nums = 0;
        for (int i = 3; i <= target; i++) {

            nums = pre_1 + pre_2;
            pre_2 = pre_1;
            pre_1 = nums;
        }

        return nums;
    }