Pointer expression.

[InvariantLoop]

I have two functions. Both give the same result. I understand how the first function works but what happens on the second function?

/* function definition */
int DataAdd1(int list[][5], int max1, int max2)
{
	int i,j;
	int sum=0;

	for(i=0; i<max1; i++)
		for(j=0; j<max2; j++)
			sum +=list[i][j];
		return sum;
}
/* function defintion*/
int DataAdd2(int *list, int max1, int max2)
{
	int i,j;
	int sum =0;
	
	for(i=0; i<max1; i++)
		for(j=0; j<max2; j++)
			sum +=*(list +i*max2 +j);
		return sum;
}

how does this

sum +=*(list +i*max2 +j);

come out to equal this

sum +=list[i][j];

i dont get it.

[Karthur]

Your question reverses the order of the two forms from the the way the code shows them , but to answer it:

In the first one, list is the address of list, max2 is the length of an i-row (in index units which are each ints in this case), i is the number of them to skip ahead, so list + i * max2 addresses the start of the i-th row, adding j indexes further to the j-th element. Note that i and j are both zero-based so the "first" row or element is the zeroth row or element. The * in front of the parentheses "dereferences" the address to get the actual int

List[i][j] refers to the j-th element in the i-th row more obviously, but possibly less efficiently (though compiler optimization should make them about the same now, this wasn't the case in early compilers).