how can I solve Pseudocode + function

if condition of function f开发者_Go百科 :

function f(x : integer) : integer;
begin
if x = 1 then
f = 0
else
f = x * f(x - 1) + x^2
end;

find value of f(4)

show me the step by step for calculate please

sorry for my poor english..

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In a real language (Python) your code would be written as follows:

def f(x):
    return 0 if x == 1 else x * f(x - 1) + pow(x, 2)

Going Down

Lets assume we start with x=4

f(4) = 4 * f(3) + 16

So we nee to evaluate f(3)

f(3) = 3 * f(2) + 9

and then evaluate f(2)

f(2) = 2 * f(1) + 4

Again we need f(1)

f(1) = 0

Coming Back Up

Now we have all the values we need we can go back up the stack of expressions:

f(2) = 2 * 0 + 4 = 4

f(3) = 3 * 4 + 9 = 21

f(4) = 4 * 21 + 16 = 100