fig06_09.cpp

c++大学教程第5版的配套书源代码

// Fig. 6.9: fig06_09.cpp
// Roll a six-sided die 6,000,000 times.
#include <iostream>
using std::cout;
using std::endl;

#include <iomanip>
using std::setw;

#include <cstdlib> // contains function prototype for rand
using std::rand;

int main()
{
   int frequency1 = 0; // count of 1s rolled
   int frequency2 = 0; // count of 2s rolled
   int frequency3 = 0; // count of 3s rolled 
   int frequency4 = 0; // count of 4s rolled
   int frequency5 = 0; // count of 5s rolled
   int frequency6 = 0; // count of 6s rolled

   int face; // stores most recently rolled value

   // summarize results of 6,000,000 rolls of a die
   for ( int roll = 1; roll <= 6000000; roll++ ) 
   {
      face = 1 + rand() % 6; // random number from 1 to 6

      // determine roll value 1-6 and increment appropriate counter
      switch ( face ) 
      {
         case 1:          
            ++frequency1; // increment the 1s counter
            break;
         case 2:          
            ++frequency2; // increment the 2s counter
            break;
         case 3:          
            ++frequency3; // increment the 3s counter
            break;
         case 4:         
            ++frequency4; // increment the 4s counter
            break;
         case 5:          
            ++frequency5; // increment the 5s counter
            break;
         case 6:         
            ++frequency6; // increment the 6s counter
            break;
         default: // invalid value
            cout << "Program should never get here!";
      } // end switch 
   } // end for 

   cout << "Face" << setw( 13 ) << "Frequency" << endl; // output headers 
   cout << "   1" << setw( 13 ) << frequency1 
      << "\n   2" << setw( 13 ) << frequency2 
      << "\n   3" << setw( 13 ) << frequency3 
      << "\n   4" << setw( 13 ) << frequency4 
      << "\n   5" << setw( 13 ) << frequency5
      << "\n   6" << setw( 13 ) << frequency6 << endl;
   return 0; // indicates successful termination
} // end main


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