Question

我需要帮助学校的课程。我们必须编写一个程序，询问用户有关棒球运动员的信息。我们需要计算球员击球平均值，比赛次数，击球次数和击球次数。我遇到一个问题，我的平均值计算输出一组数字而不执行任何计算。我正在为所有用于计算的变量输入整数。所以我会输入数字，如1,4,10等...由于程序代表我的公式设置自己等于的值是15903.876。用于平均公式的所有变量都被声明为整数，而击球平均值本身被声明为双精度。我做了一些自我调试，发现当它将击球次数除以击中次数时，计算会混乱。如果有人能帮我解决这个问题，我会很感激。

//libaries
#include <iostream>
#include <string>
#include <sstream>
#include <iomanip> 
using namespace std;

class battingAverage
{
public:

  string pName;
  int nBats;
  int tHits;
  int gPlayed;
  int gcalled;
  double average;
  double average1;
  double playeraverage;

};

int main()
{
   string numberPlayers;
  int nplayers;
 //enters the number of players the user wants to enter data for
 cout << "Enter the number of players you want to enter data for: ";
 cin >> numberPlayers;
 cout << endl;

//converts the value of numberPlayers to nplayers
istringstream convert(numberPlayers);

//sets integer nplayers equal to the value of the string numberPlayers
if(! (istringstream(numberPlayers) >> nplayers) )
{
    nplayers = 0;
}

cout << "This program calculates the batting average of baseball players.\nYou may enter data for " << nplayers << " players." << endl;

battingAverage ba[nplayers];

int index = 0;

//while statement to get data
while(index < nplayers)
{
  cout << "Enter the players last name: " << endl;
  cin >> ba[index].pName;

  cout << "Enter the number of games the player played: " << endl;
  cin >> ba[index].gPlayed;
  cout << ba[index].gPlayed << endl;

  cout << "Enter the number of games the player was called in for: " << endl;
  cin >> ba[index].gcalled;
  cout << ba[index].gcalled << endl;

  cout << "Enter the number of times the player was at bat: " << endl;
  cin >> ba[index].nBats;
  cout << ba[index].nBats << endl;

  cout << "Enter the number of time the player hit: " << endl;
  cin >> ba[index].tHits;
  cout << ba[index].tHits << endl;

  if(ba[index].tHits > ba[index].nBats)
  {
    cout << "Enter a valid value for the number of times the player hit: ";
    cin >> ba[index].tHits;
  }

  cout << endl;
  index++;

}

//rounds average to 3 decimal places
cout << fixed << setprecision( 3 );
//average formula
ba[index].playeraverage = (ba[index].nBats / ba[index].tHits) * (ba[index].gPlayed / ba[index].gcalled);//error
cout << ba[index].playeraverage << endl << endl;//just temp line to check calculation of average.

ba[index].average = .000;
ba[index].average1 = .099;

 while(ba[index].average < 1 && ba[index].average1 < .899)
{
    ba[index].average +=.100;
    ba[index].average1 += .1;
    //prints chart
    cout << setprecision( 1 ) << ba[index].average  << "00" << setprecision( 3 ) << setw(12) << ba[index].average1 << endl;
    }

cout << "1.000" << setw(12) << "1.000" << endl;

//version of system pause
cout << "\nPress enter to continue...";
cin.sync();
cin.ignore();
return 0;

}

Answer 1

在这一行：

ba[index].playeraverage = (ba[index].nBats / ba[index].tHits) * (ba[index].gPlayed / ba[index].gcalled);//error

你有这个表达：

(ba[index].nBats / ba[index].tHits)

因为nBats和tHits都是整数，所以你只使用整数数学答案是整数。

例如：
nBats = 10＆amp; tHits = 3，您希望表达式为3.333 但它只是3

要解决此问题，建议您更改为：

((double)ba[index].nBats / ba[index].tHits)

关于gPlayed和gcalled的表达式再次相同。

Answer 2

在计算过程中，您的索引值是错误的。

一旦我将您的代码放入调试器并逐步完成它，我发现了这一点，真正应该自己完成。

您从int index = 0;开始，并在用户输入每个玩家的数据时递增它。在输入循环结束时，索引现在与玩家数量相同 （例如，如果你有5个玩家，索引现在是5，玩家数据存储在ba[0]，ba[1]，ba[2]，ba[3]和{ {1}}）

请注意，此时ba[4]是 NOT 有效数据。但这正是ba[5]所在的地方！

你在ba[index]上做了所有的计算，这是无效的数据，你想知道为什么你会得到毫无意义的结果？

我建议您在开始计算之前将索引设置回0，并为每个玩家0 ... 4制作另一个循环，以进行必要的计算。

棒球击球平均计划

2 个答案: