Programming Puzzle in C++ Language?

Question

Dear friends, one of my friends asked me a programming puzzle yesterday, but I dont know the answer!

We have a piece of code in C++ language:

#include <iostream>

using namespace std;

int main() {

int a;

cin >> a;

if ( ( a == -a ) && ( a != 0) )

cout << ":-o" << endl;

return 0;

}

If we want the program print something as an output on the monitor, what should we give as an input???!

Answer 1

-2147483648 (-(2^31) or more generally -(2^(n-1)) where n is the number of bits in the integer type).

Binary representation is

10000...0000

-a in two&#039;s complement is

1. invert

01111...1111

2. Add one

10000...0000

a=-a (and a != 0)