ex18_20.cpp

《c＋＋大学教程》源码

// Exercise 18.20: ex18_20.cpp
#include <iostream>

using std::cout;
using std::cin;
using std::endl;
using std::boolalpha;

bool mystery( unsigned );

int main()
{
   unsigned x;

   cout << "Enter an integer: ";
   cin >> x;
   cout << boolalpha 
        << "The result is " << mystery( x ) << endl;

   return 0;

} // end main

// What does this function do?
bool mystery( unsigned bits )
{
   const int SHIFT = 8 * sizeof( unsigned ) - 1;
   const unsigned MASK = 1 << SHIFT;
   unsigned total = 0;

   for ( int i = 0; i < SHIFT + 1; i++, bits <<= 1 )

      if ( ( bits & MASK ) == MASK ) 
         ++total;

   return !( total % 2 );

} // end function mystery

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