NIM game

[towjam]

Can someone explain to me in great detail what is goin on in this loop.It's pretty simple but i can't seem to fully understand the bottom half(the second loop).




Basiclly this function will display this pattern (which is used when playing NIM) :-
|
| |
| | |
| | | |
| | | | |



Also the variable "a" just point at an array , which is :-

int row[6] = {0, 1, 2, 3, 4, 5};





Example -- when i call this function , i would go like this

display (row)

void display(int* a)
{
cout << "|-----------------------------|\n";
for(int i = 0; i < 6; i++)
{
if(i==1) cout << " ";
if(i==2) cout << " ";
if(i==3) cout << " ";
if(i==4) cout << " ";
if(i==5) cout << " ";

for(int j =1; j <= *a; j++)
cout << " |";
a++;
cout << "\n\n";
}
cout << "\n|-----------------------------|\n";
}


So if someone understands this please reply
thanks in advance

 

[tsh73]

If I understand correctly...
You have two loops nested
First loop counts rows
"if" things puts spaces in the beginning of a row
so you would get
" | "
"| |"
instead of just
"| "
"| |"
second loop - inside one - prints " |" several times, there "several" is taken from array a.
(that is all this loop do - one line).
so *a is current array item (starting from the 0th )
And "a++" instruction advances to the next item.

Hope this helps.

 

[itsgsd]

It really helps to read the code if you put the [ignore]

[/ignore] tags around it.

I hope I'm understanding your question:

What is happening in your second loop (and just after) is pointer dereferencing and classic pointer arithmetic.

As you know, a pointer points to some area in memory. In this case the pointer a points to the memory that stores the integer array row. Dereferencing a pointer (*a) simply means getting the value that the pointer points to.

The first time through the loop, the pointer a points to the beginning of the array row. *a means the data at the memory location pointed to by pointer a, so the first time through the loop, *a holds the value 0 (which simply results in two blank lines printing). You then increment a (a++ which is your pointer arithmetic) and a now points to the 2nd array element and *a now gives the value 1. This process continues through the entire array with *a next giving the value 2 then 3 then 4 then 5.

So stepping through the loop:
[tt]
{0,1,2,3,4,5}
|
a [red]*a == 0, loop evaluates to: for (j=1; j <= 0; j++)[/red]

now a++
{0,1,2,3,4,5}
|
a [red]*a == 1, loop evaluates to: for (j=1; j <= 1; j++)[/red]

now a++
{0,1,2,3,4,5}
|
a [red]*a == 2, loop evaluates to: for (j=1; j <= 2; j++)[/red]

and so on...
[/tt]

Hope that answered your question.

 

[itsgsd]

tsh73, looks like we were drafting answers at the same time. towjam, yes, it's just like tsh73 said.

 

[towjam]

Thanks everybody , that really helped