tortoiseandhare.cpp

C++上机课的习题答案

// Chapter 5 of C++ How to Program
// tortoiseandhare.cpp
// 龟兔赛跑
//注意按指针（按址）传递参数来调用函数。
//当y为5时，兔子往前跑，其余则不动（睡觉）来模拟兔子的行为 
#include <iostream>

using std::cout;
using std::endl;

#include <cstdlib>

#include <ctime>

#include <iomanip>

using std::setw;

const int RACE_END = 70;

/* Write prototype for moveTortoise here */
/* Write prototype for moveHare here */
/* Write prototype for printCurrentPositions here */

int main()
{
   int tortoise = 1; 
   int hare = 1;
   int timer = 0;

   srand( time( 0 ) );

   cout << "ON YOUR MARK, GET SET\nBANG !!!!"//各就各位
        << "\nAND THEY ARE OFF !!!!\n";
   
   // controls race
   while ( tortoise != RACE_END && hare != RACE_END ) {
      /* Write call for moveTortoise here */
      /* Write call for moveHare here */
      /* Write call for printCurrentPositions here */    
      ++timer;

   } // end while

   // determine winner
   if ( tortoise >= hare )
      cout << "\nTORTOISE WINS!!! YAY!!!\n";

   else
      cout << "Hare wins. Yuch.\n";

   cout << "TIME ELAPSED = " << timer << " seconds" << endl;

   system("PAUSE");
   return 0;   
} // end main

// move tortoise
/* Write function definition header for moveTortoise here */
{
   int x = 1 + rand() % 10;

   // determine which move to make
   if ( x >= 1 && x <= 5 )        // fast plod（快走） 
      *turtlePtr += 3;

   else if ( x == 6 || x == 7 )   // slip（滑倒） 
      *turtlePtr -= 6;

   else                           // slow plod（慢走） 
      ++( *turtlePtr );
   
   // ensure that（确保） tortoise remains within subscript range（下标） 
   if ( *turtlePtr < 1 )
      *turtlePtr = 1;

   else if ( *turtlePtr > RACE_END )
      *turtlePtr = RACE_END;

} // end function moveTortoise

// move hare
/* Write function definition for moveHare here */
{
   int y = 1 + rand() % 10;

   /* Write statements that move hare */

   /* Write statements that test if hare is before
      the starting point or has finished the race */

} // end function moveHare

// output positions of animals
/* Write function definition for printCurrentPositions here */
{
   if ( *bunnyPtr == *snapperPtr ) //bunny:小兔子 
      cout << setw( *bunnyPtr ) << "OUCH!!!";      

   else if ( *bunnyPtr < *snapperPtr ) 
      cout << setw( *bunnyPtr ) << "H" 
           << setw( *snapperPtr - *bunnyPtr ) << "T";

   else
      cout << setw( *snapperPtr ) << "T" 
           << setw( *bunnyPtr - *snapperPtr ) << "H";

   cout << "\n";

} // end function printCurrentPositions