Hello,

I'm trying to solve an ACM problem "Light, more light". The problem is actually solved, but I can get it accepted. So browsing Internet I found a C code, which is accepted:

#include<stdio.h>
#include<math.h>

int main(void) {
	long long int n;
	while(scanf("%lld", &n)==1) {
		if(n==0)
			break;
		else if( (long long int)sqrt((double)n) * (long long int)sqrt((double)n) == n)
			printf("yes\n");
		else
			printf("no\n");
	}
	return 0;
}

However, it doesnt' work in Eclipse's console (MinGW GCC toolchain). Why is that?

But the main problem is not that. The task states, that the number won't exceed 2^32 - 1, so in my own solution I used unsigned int:

#include <stdio.h>
#include <math.h>

int main() 
{		
	unsigned int n;	
	while (scanf("%d", &n) == 1)
	{			
		if (n == 0) 
			break;
		else 
		{
			unsigned int root = (unsigned int)sqrt((double)n); 
			if (root*root != n) 
			{	
				printf("no\n");
			}
			else 
			{
				printf("yes\n");
			}			
		}
		
	}
	
	return 0;
}

... which is almost the same, works fine in Eclipse's console, but doesn't get accepted on ACM neither as ANSI C, nor as C++. Can anyone tell me where is the mistake?

what are the errors when you attempt to compile on ACM?

Is simply says "Wrong answer".

the problem with the code using unsigned it is that nowhere in the c++ standard does it say std::numeric_limits<unsigned int>::max() >= 2^32 - 1 or for that matter, std::numeric_limits<unsigned int>::radix == 2 or std::numeric_limits<unsigned int>::digits >= 32 .
so the code may fail for some input values on some implementations.

the code that was accepted is neither ISO C++ nor ANSI C. neither talks about a type long long.
the C99 standard introduced the long long int type ( to be an integral type with at least 64 bits) and it is a long-supported extension by almost all compilers. (C++0x adds this type as well as unsigned long long as fundamental types). by now, long long int (abbreviated as long long) has become a de facto standard (it is de jure only in C99). which is probably why it was accepted.