Programming question

[luvlyvee]

Hello. I am a beginner in programming and wanted to know if someone can help. I have no idea what I am doing or where to even start. If anyone can help me on where to begin I would appreciate it. Here is the assignment.

What does the following program do?. Copy the sample program and compile it, then find the results. Submit a report which is more than one page length to explain how the program works and how you can improve it.

The problem is I don't even know what is wrong with the program? I understand that it adds up all the numbers but am I supposed to put in the program that it is supposed to add up the numbers?

#include <iostream>
using std::cout;
using std::endl;

int whatIsThis( int [], int ); //funtion prototype

int main()
{
const int arraySize = 10;
int a[ arraySize ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

int result = whatIsThis( a, arraySize);

cout << "Result is" << result << endl;
return 0; //indicates succesful termination
} // end main

// What does this function do?
int whatIsThis( int b[], int size)
{
if ( size == 1 ) // base case
return b [ 0 ];
else // recursive step
return b [ size - 1 ] + whatIsThis( b, size - 1 );
} //end function whatIsThis

[48T7M4Gy]

http://www.cplusplus.com/forum/beginner/176922/
http://www.cplusplus.com/forum/windows/176924/
http://www.cplusplus.com/forum/general/176928/

[Ericool]

recursive function ( it calls itself) basically it calculat the sum of all element in the array and put it in the first element the. return the value of the first elemtn( the sum)

[luvlyvee]

Ok. Thank you. If I understand you correctly this program no matter what numbers I enter, it will calculate the sum? So I don't have to write out each number?

[48T7M4Gy]

try int a[ arraySize ] = { 112, 107, -219, 1 };

[48T7M4Gy]

Not now. But please avoid multiple postings on the same question. Once is enough to get a reply.

I hope you tried the suggestion with changing the numbers.

[luvlyvee]

I played around with the numbers and even changed the size. I changed the 10 to a 5. I used kemort's example in which after I ran the program I got a 1. I put in my own numbers and got the same results too.

int main()
{
const int arraySize = 5;
int a[ arraySize] = { 112, 107, -219, 1 };
int result = whatIsThis( a, arraySize);

cout << "Result is" << result << endl;
return 0; //indicates succesful termination
} // end main

int main()
{
const int arraySize = 10;
int a[ arraySize] = { 200, 150, -350, 1 };
int result = whatIsThis( a, arraySize);

cout << "Result is" << result << endl;

[luvlyvee]

Ok will do. I never used this forum before. Thank so much for the feedback! Yes I did. I changed several of the numbers to see what kind of results I would get. It seems that if I add the (-) in front of an integer it's going to still provide me with the sum but subtract from the other numbers. When I changed the arraySize I did not see much of a difference unless I did something wrong.

[48T7M4Gy]

Great stuff. The array is a container for the list of numbers and the program goes though each number to give their total. That's why you got 1 as the answer. Try 1,2,3,4 and you should get 10.

Changing arraySize changes the size of the container and not the numbers themselves. So there's nothing much to immediately see. There's a tutorial here on this site where you can look up if you want more info on arrays. :)

PS and putting a - in front of a number makes it negative which has the effect of subtracting the number from the total in this case.

[luvlyvee]

Aahh. Great. Thanks for explaining it that way! Makes much more sense now as I am changing the numbers. I appreciate all of your help! I'm going to work on finishing it up and then can post my final source code. Thanks again :-)

[48T7M4Gy]

We all look forward to the final result. Post it here when you're ready.

[luvlyvee]

Here is what I came up with. It seems to run better. I took your advise about the arrays after I reviewed the tutorial. Hope this is what the professor is looking for :-)

#include <iostream>
using namespace std;

int main()
{

int size;
double sum = 0;
cout << "I'll tell you sum of numbers. \n" ; // user will be prompted to decide how many numbers they want to enter
cout << "\nHow many numbers do you wish to find?"; //user will be prompted to input the number
cin >> size; // will display the user input

// allocates the array
int * array = new int[size];

// first loop - get the data
for (int count=0; count<size; count++)
{
cout << "Enter Number: "; // user will be prompted to enter the first number, second nmbr, etc until max is 10
cin >> array[count]; //inputs the numbers that the user entered
}

// second loop - accumulate the total
for (int count=0; count<size; count++)
sum += array[count]; //calculates all of the numbers that the user enters

cout << "The sum is " << sum << endl; // the results are displayed of all numbers entered


// de-allocate the array
delete [] array;

return 0; // indicates successful termination of the program
}

[48T7M4Gy]

Looks pretty good. One small point, cin doesn't display the user input, your comment on the second cin statement is a better description of cin workings.

I hope you get good marks :)