5 replies to this topic

[Faint545]

I've been searching the web for a sum fucntion but I just can't seem to find one...

I'm programming in C++ and I have an array of numbers ( name[#] ) and I would like to calculate the sum of them without typing out the positions individually. Is there any way that is possible?

[yordan]

If you are running C++, you should have no problem writing down a loop
Sum=1
while blah...
++sum

No ?

[mastercomputers]

Here's something I came up with

#include <iostream>

int sum(int arr[], int length){
	int sum = 0;
	for(int i = 0, n = length; i < n; i++){
		sum += arr[i];
	}
	return sum;
}

int main(){
	int test[] = { 1, 2, 3, 4, 5 };
	int result = sum(test, sizeof(test)/sizeof(int));
	std::cout << result << std::endl;
	return 0;
}

The problem with sending an array to a function is that the size information is lost, so you must send the size yourself. That is why I used sizeof(array)/sizeof(int); to work out the size of it.

Cheers,


MC

[bluefish]

You could also use the STL algorithm 'accumulate':

#include <algorithm>
#include <iostream>
//...
int main(){
	int test[] = { 1, 2, 3, 4, 5 };
	int result = std::accumulate(test, test + 5);
	std::cout << result << std::endl;
	return 0;
}

It takes a pointer or iterator to the start of a sequence and a pointer of iterator one past the end of the sequence. Simply put, the first argument is the name of the array and the second is the name of the array plus the size of the array. You can also use it for STL containers, as in:

#include <algorithm>
#include <iostream>
#include <vector>
//...
int main(){
	std::vector<int> test(4,9);
	int result = std::accumulate(test.begin(), test.end());
	std::cout << result << std::endl;
	return 0;
}

Edited by bluefish, 16 December 2006 - 06:16 PM.

[ignite]

If you are running C++, you should have no problem writing down a loop
Sum=1
while blah...
++sum

No ?

You did some mistake. Actually you wrote in pseudocode count function. Sum differ from what you wrote in first line: Sum = 0, then in third Sum +=
Here is simple one line example code: for( float Sum=0, int i=0; i<sizeof(array); i++) Sum+=array[i];

[yordan]

You did some mistake. Actually you wrote in pseudocode count function. Sum differ from what you wrote in first line: Sum = 0, then in third Sum +=
Here is simple one line example code: for( float Sum=0, int i=0; i<sizeof(array); i++) Sum+=array[i];

Ouch ! yes, you are right. I could imagine that, before starting, the sum is 0, and I started with Sum=1.
You know, a lot of people did this mistake some years ago.
They really thought that January 1st 2000 was the beginning of the new century. And that's false, it was the beginning of the last year of the old century.
Still the same problem : how do you count the things in your pocket : 1 - 2 - 3 - 4, or 0 - 1 - 2 -3 ?