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1.00/5 (1 vote)
See more:
C++
```#include<stdio.h>
int main()
{
int n,i,a[10000],c[10000],j;
scanf("%d",&n);
if(n<=1000)
{
for(i=0;i<2*n;i++)
{
scanf("%d",&a[i]);
}
for(j=0,i=0;i<2*n,j<n;i=2*j+2,j++)
{
c[j]=(a[i]*a[i+1]);
}
for(i=0;i<n;i++)
printf("%d\n",c[i]);
return 0;
}
}```

What I have tried:

tried to fulfil every condition asked in problem

tested the test sample condition it worked absoulutely fine

SPOJ.com - Problem MUL[^]
Posted
Updated 4-Jun-20 1:13am
v5
Richard MacCutchan 4-Jun-20 6:27am

Please edit your question and explain what the problem is. What output do you see and why is it not correct?
KarstenK 4-Jun-20 13:53pm

Use the debugger and make some print output in the second for loop to see your mess.

## Solution 2

Quote:
tried to fulfil every condition asked in problem

No, you didn't. Read again, numbers to multiply are up to 10000 digits each.
Quote:
tested the test sample condition it worked absoulutely fine

Yes, because sample input fits int standard integers. There is no way for a 10000 digits integer to fit in a standard integer variable.
Either you use BigInt library or recreate equivalent.

There is no correction because the program simply don't fit the problem.

This loop
C++
`for(j=0,i=0;i<2*n,j<n;i=2*j+2,j++)`

is complicated for nothing, and can be simplified to
C++
`for(i=0;i<2*n;i+=2)`
v2
Member 14849246 4-Jun-20 7:23am

so how to store such a big number of 10000 digit should we use long long int ? what is bigint library?
Patrice T 4-Jun-20 7:47am

## Solution 1

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:
```Input   Expected output    Actual output
1            2                 1
2            4                 4
3            6                 9
4            8                16```
Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:
C#
```int Double(int value)
{
return value * value;
}```

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.

If you don't know how to use the debugger, then Google for the name of your IDE (the Integrated Development Environment in which you edit, compile and test your code) plus the word "Debugger" and it will find you instructions.

This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!