1. I don't know what you want to output, so I only output the final result. The key steps are all written. Just call the f0 () function, mainly using the recursion of the function.

Function y=f0(x)

% Enter an integer from the keyboard. Divide the even number by 2 and the odd number by *3+ 1 until 1.

If x== 1

y = 1；

elseif mod(x，2)==0

x = x/2；

y = F0(x)；

elseif mod(x，2)== 1

x = x * 3+ 1；

y = F0(x)；

other

X=' input error';

disp(X)；

end

2. I use matrix equation to solve the problem directly. The function is F 1 (X 1, X2), where X 1 is the head number and x2 is the foot number.

The function y=f 1(x 1, x2)

%x 1 is the number of heads, and x2 is the number of feet.

a =[ 1 1； 2 4];

a =[x 1； x2]；

y = a \ A

3. A formula can solve this problem:

y=abs(x)+abs(x-2)

%abs(x) is a function of finding the absolute value.

Or call this function.

Function y=f2(x)

%y=|x|+|x-2|

y = ABS(x)+ABS(x-2)；

PS: The most important thing is that you have to learn by yourself.