I have a problem with a code which works on my laptop but not on sololearn

Question

#include <iostream>
using namespace std;
#include <stdio.h>
#include <stdlib.h>
#include<ctype.h>

int main()
{
char c;
printf("ENTER TEXT !\n");
while(c=getchar())
if(isupper(c))
putchar(tolower(c));
else
putchar(toupper(c));
return 0;
}

Answer 1

Although it looks messy, I think it'll do. scanf is not working in code playground.
Give your input like:
b
M
s
0

https://code.sololearn.com/cb9w5MWL6Dgn/?ref=app

Answer 2

duplicate post (~30m gap)
https://www.sololearn.com/Discuss/844912/?ref=app

The implementation here is batch, not interactive. Sometimes I recommend a dummy function to signal SoloLearn's input box:

void dummy(){ char x; cin >> x; } // never called

But your code relies on reading a NULL byte to end, which (going on short tests here) isn't sent in the batched character stream / pipe.