Accelerated C++之计算学生成绩3

层层深入，由浅及深
一个例子，包含多少知识点，自己看哦

第三部分

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• median.h

#ifndef GUARD_median_h//检查头文件GUARD_median_h是否被定义，//如果未定义，就会请求预处理程序对在他和#endif之间的所有内容作出适当的处理动作//名称要唯一#define GUARD_median_h//.h中不能包含using声明#include <vector>double median(std::vector<double>);#endif

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• median.cc

#include <algorithm>#include <iostream>#include <stdexcept>#include <vector>#include "median.h"using namespace std;double median(vector<double> vec){    typedef vector<double>::size_type vec_sz;    vec_sz size = vec.size();    if (size == 0)        throw domain_error("median of an empty vector");    sort(vec.begin(), vec.end());    vec_sz mid = size / 2;    return size % 2 == 0 ? (vec[mid] + vec[mid - 1]) / 2 : vec[mid];}

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• Student_info.h

#ifndef GUARD_Student_info#define GUARD_Student_info#include <string>#include <vector>struct Student_info{    std::string name;    double midterm, final;    std::vector<double> homework;};bool compare(const Student_info& , const Student_info&);std::istream& read(std::istream&, Student_info&);std::istream& read_hw(istream&, std::vector<double>&);#endif

• Student_info.cc

#include "Student_info.h"#include <iostream>using namespace std;bool compare(const Student_info& x, const Student_info& y){    return x.name < y.name;}istream& read(istream& is, Student_info &s){    double midterm, final;    is >> s.name >> midterm >> final;    read_hw(is, s.homework);    return is;}istream& read_hw(istream& in, vector<double>& hw){    if (in)    {        hw.clear();        double x;        while (in >> x)            hw.push_back(x);        in.clear();    }    return in;}

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• grade.h

#ifndef GUARD_grade_h#define GUARD_grade_h#include <vector>#include "Student_info.h"double grade(double, double, double);double grade(double, double, const std::vector<double>&);double grade(const Student_info&);#endif

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• grade.cc

#include <iostream>#include <stdexcept>#include <vector>#include "grade.h"#include "median.h"#include "Student_info.h"using namespace std;double grade(double midterm, double final, double homework){    return 0.2 * midterm + 0.4 * final + 0.4 * homework;}double grade(double midterm, double final, const vector<double>& hw){    if (hw.size() == 0)        throw domain_error("student has done no homework");    return grade(midterm, final, median(hw));}double grade(const Student_info& s){    return grade(s.midterm, s.final, s.homework);}

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• main.cc

#include <algorithm>#include <iomanip>#include <vector>#include <iostream>#include <stdexcept>#include <string>#include "grade.h"#include "Student_info.h"using namespace std;int main(){    vector<Student_info> students;    Student_info record;    string::size_type maxlen = 0;    while (read(cin, record))    {        maxlen = max(maxlen, record.name.size());        students.push_back(record);    }    // 按照顺序排列学生记录    sort(students.begin(), students.end(), compare);    for (vector<Student_info>::size_type i = 0; i != students.size(); ++i)    {        // 输出姓名，把姓名填充至maxlen+1个字符长度        cout << students[i].name<< string(maxlen + 1 - students[i].name.size(), ' ');        try        {            double final_grade = grade(students[i]);            streamsize prec = cout.precision();            cout << setprecision(3) << final_grade << setprecision(prec);        } catch (domain_error e)        {            cout << e.what();        }        cout << endl;    }    return 0;}

未完待续