程序实践系列之利用2D数组的GradeBook类
介绍类GradeBook,使用一个二维数组存储学生在多次考试所得的成绩.在一个学期中,学生很可能参加多次考试,老师也可能希望分析一个学生或整个班级在整个学期所获得成绩.即:在GradeBook二维数组中存储学生成绩.程序如下所示:
二维数组存储学生成绩类GradeBook的定义
//Definiton of class Gradebook that uses a two-dimesion array to store test grades
#include //program uses C++ Standard Library string class
using namespace std;
#ifndef GRADEBOOK_H
#define GRADEBOOK_H
//GradeBook class definition
class GradeBook {
public:
//constants
static const int students =10; //number of students
static const int tests = 3; // number of tests
//constructor inititalizes cousre name and array of grades
GradeBook(string, const int [][ tests]);
void setCourseName( string); // function to set the course name
string getCourseName(); // function to retrieve the course name
void displayMessage(); // display a welcome message
void processGrades(); // perform various operations on the grade data
int getMinimum(); //find the minimum grade in the grade book
int getMaximum(); //find the maximum grade in the grade book
double getAverage (const int[] , const int); // get student's average
void outputBarChart(); // output bar char of grade distriudbution
void outputGrades(); // output the constanets of the grades array
private:
string courseName ; // course name for this grade book
int grades[students][tests]; // two-dimensional array of grades
}; // end class
#endif // 操作二维数组的GradeBook类成员函数的定义
// Member-function definitions for class GradeBook that
// uses a two-dimensional array to store grades.
#include
using std::cout;
using std::cin;
using std::endl;
using std::fixed;
#include // parameterized stream manipulators
using std::setprecision; // sets numeric output precision
using std::setw; // sets field width
// include definition of class GradeBook from GradeBook.h
#include "GradeBook.h"
// two-argument constructor initializes courseName and grades array
GradeBook::GradeBook( string name, const int gradesArray[][ tests ] )
{
setCourseName( name ); // initialize courseName
// copy grades from gradeArray to grades
for ( int student = 0; student < students; student++ )
for ( int test = 0; test < tests; test++ )
grades[ student ][ test ] = gradesArray[ student ][ test ];
} // end two-argument GradeBook constructor
// function to set the course name
void GradeBook::setCourseName( string name )
{
courseName = name; // store the course name
} // end function setCourseName
// function to retrieve the course name
string GradeBook::getCourseName()
{
return courseName;
} // end function getCourseName
// display a welcome message to the GradeBook user
void GradeBook::displayMessage()
{
// this statement calls getCourseName to get the name of the course this GradeBook represents
cout << "Welcome to the grade book for\n" << getCourseName() << "!" << endl;
} // end function displayMessage
// perform various operations on the data
void GradeBook::processGrades()
{
// output grades array
outputGrades();
// call functions getMinimum and getMaximum
cout << "\nLowest grade in the grade book is " << getMinimum()
<< "\nHighest grade in the grade book is " << getMaximum() << endl;
outputBarChart();// output grade distribution chart of all grades on all tests outputBarChart();
} // end function processGrades
// find minimum grade
int GradeBook::getMinimum()
{
int lowGrade = 100; // assume lowest grade is 100
for ( int student = 0; student < students; student++ ) // loop through rows of grades array
{
for ( int test = 0; test < tests; test++ ) // loop through columns of current row
{
if ( grades[ student ][ test ] < lowGrade ) // if current grade less than lowGrade, assign it to lowGrade
lowGrade = grades[ student ][ test ]; // new lowest grade
} // end inner for
} // end outer for
return lowGrade; // return lowest grade
} // end function getMinimum
// find maximum grade
int GradeBook::getMaximum()
{
int highGrade = 0; // assume highest grade is 0
// loop through rows of grades array
for ( int student = 0; student < students; student++ )
{
// loop through columns of current row
for ( int test = 0; test < tests; test++ )
{
// if current grade greater than lowGrade, assign it to highGrade
if ( grades[ student ][ test ] > highGrade )
highGrade = grades[ student ][ test ]; // new highest grade
} // end inner for
} // end outer for
return highGrade; // return highest grade
} // end function getMaximum
// determine average grade for particular set of grades
double GradeBook::getAverage( const int setOfGrades[], const int grades )
{
int total = 0; // initialize total
// sum grades in array
for ( int grade = 0; grade < grades; grade++ )
total += setOfGrades[ grade ];
return static_cast< double >( total ) / grades; // return average of grades
} // end function getAverage
// output bar chart displaying grade distribution
void GradeBook::outputBarChart()
{
cout << "\nOverall grade distribution:" << endl;
// stores frequency of grades in each range of 10 grades
const int frequencySize = 11;
int frequency[ frequencySize ] = { 0 };
// for each grade, increment the appropriate frequency
for ( int student = 0; student < students; student++ )
for ( int test = 0; test < tests; test++ )
++frequency[ grades[ student ][ test ] / 10 ];
// for each grade frequency, print bar in chart
for ( int count = 0; count < frequencySize; count++ )
{
// output bar label ("0-9:", ..., "90-99:", "100:" )
if ( count == 0 )
cout << " 0-9: ";
else if ( count == 10 )
cout << " 100: ";
else
cout << count * 10 << "-" << ( count * 10 ) + 9 << ": ";
// print bar of asterisks
for ( int stars = 0; stars < frequency[ count ]; stars++ )
cout << '*';
cout << endl; // start a new line of output
} // end outer for
} // end function outputBarChart
// output the contents of the grades array
void GradeBook::outputGrades()
{
cout << "\nThe grades are:\n\n";
cout << " "; // align column heads
// create a column heading for each of the tests
for ( int test = 0; test < tests; test++ )
cout << "Test " << test + 1 << " ";
cout << "Average" << endl; // student average column heading
// create rows/columns of text representing array grades
for ( int student = 0; student < students; student++ )
{
cout << "Student " << setw( 2 ) << student + 1;
// output student's grades
for ( int test = 0; test < tests; test++ )
cout << setw( 8 ) << grades[ student ][ test ];
// call member function getAverage to calculate student's average;
// pass row of grades and the value of tests as the arguments
double average = getAverage( grades[ student ], tests );
cout << setw( 9 ) << setprecision( 2 ) << fixed << average << endl;
} // end outer for
} // end function outputGrades 测试GradeBook类
// TestMain.cpp
// Creates GradeBook object using a two-dimensional array of grades.
#include "GradeBook.h" // GradeBook class definition
// function main begins program execution
int main()
{
// two-dimensional array of student grades
int gradesArray[ GradeBook::students ][ GradeBook::tests ] =
{ { 87, 96, 70 },{ 68, 87, 90 },
{ 94, 100, 90 },{ 100, 81, 82 },
{ 83, 65, 85 },{ 78, 87, 65 },
{ 85, 75, 83 },{ 91, 94, 100 },
{ 76, 72, 84 },{ 87, 93, 73 } };
GradeBook myGradeBook(
"C++ Programming Practice", gradesArray );
myGradeBook.displayMessage();
myGradeBook.processGrades();
return 0; // indicates successful termination
} // end main测试输出结果
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