Why I Need this If?

Question

Hello Guys, i'm new in this community and new in programming.
I have a question about c++'s program.

Why i need if in the first For? If i don't use it and if i put n<=15, the program cout 0 and after the result.
Why this?
https://code.sololearn.com/c55qASGg0YL2/?ref=app
https://code.sololearn.com/c55qASGg0YL2/?ref=app

Answer 1

Ok, thank you. Look again the code, now how the initialization is?
Another think: I can't input 0 because in the For i used n>0 and not n>=0. If i use n>=0 in the For my program crash,why this?

Answer 2

int n,i;
int arr[i];

I find this particular code segment dangerous. Variable i has not been initialized. Assuming that i is 0 at the time of initialization for arr, you have an array of size 0 and will then be writing to memory addresses that are not allocated to you. Running it on a local machine (after compiling it w/ your own compiler) may give you segfaults.

Now, moving on from the rant.

cout<<"Number:\n";
cin>>n;
for (i=0;n>0;n=n/16)
{
arr[i]=n%16;
if(n>15)
i++;
}

Here, you are trying to convert a decimal value (base 10) to a hexadecimal value (base 16). If you take a closer look at the code, this segment is the only place where you increment the value of i. The variable i is used to determine which slot of array arr you are writing to, and should be incremented for each loop iteration. However, doing so without checking the value of I will force the program to increment i at the last iteration of the loop, "initializing" an extra slot at the end.

Answer 3

(cont)

This, of course, is a sloppy fix.

Instead of using a fixed-size array, I would suggest utilizing vectors, which allow you to append elements dynamically.

Answer 4

Nothing?