Accelerated C++ 笔记第4章组织程序和数据

谁践踏了优雅 2023-06-12 08:57 17阅读 0赞

### 文章目录 ###

*  2. 组织数据
 *  待修改

# include <iostream>
    #include <iomanip>
    #include <string>
    #include<vector>
    # include <algorithm>
    # include<stdexcept>//定义了异常类型 domain_error
    using namespace std;
    
    //查找中值
    double median(vector <double> vec)
    { 
    	typedef vector <double>::size_type vec_size;
    	vec_size size = vec.size();
    	//如果向量为空，抛出异常
    	if (size == 0)
    	{ 
    		throw domain_error("empty");
    	}
    	sort(vec.begin(), vec.end());
    	vec_size mid  = size / 2;
    	
    	return size % 2 == 0 ? (vec[mid] + vec[mid - 1]) / 2 : vec[mid];
    }
    
    //计算成绩
    
    double grade(double midterm, double final, double homework)
    { 
    	return 0.2 * midterm + 0.4 * final + 0.4 * homework;
    }
    
    //const vector<double>对参数类型为double的向量常量的引用
    //引用是指 一个特定对象的另外一个名称
    double grade(double midtern, double final, const vector<double>& hw)
    { 
    	if (hw.size == 0)
    	{ 
    		throw domain_error("students have no hw");
    	}
    	return grade(midtern, final, median(hw));
    }
    
    
    //读一个输入流，把家庭作业成绩读进一个vector<double>类型的向量中
    
    istream& read_hw(istream& in, vector<double>& hw)
    { 
    	if (in)
    	{ 
    		//清除原先的内容
    		hw.clear();
    		//读家庭作业
    		double x;
    		while (in >> x)
    		{ 
    			hw.push_back(x);
    		}
    		in.clear();
    	}
    	return in;
    }
    
    int main()
    { 
    	//请求并输入学生的姓名
    	cout << "Please enter student name:" << endl;
    	string name;
    	cin >> name;
    	cout << "Hello," << name << "!" << endl;
    		
    
    	//请求并输入期中和期末的成绩
    	cout << "Please enter you midterm and final grades:" << endl;
    	double midterm, final;
    	cin >> midterm >> final;
    
    	//读入家庭作业
    	cout << "Please enter you homework ,"
    		"followed by end- of -file" << endl;
    	vector<double> homework;
    	read_hw(cin, homework);
    
    	//如果可以的话计算总成绩
    	try { 
    		double final_grade = grade(midterm, final, homework);
    		streamsize prec = cout.precision();
    		cout << "Your final grade is " << setprecision(3) << final_grade
    			<< setprecision(prec) << endl;
    	}
    	catch (domain_error)
    	{ 
    		cout << endl << "you must enter you grades" <<
    			"Please try again." << endl;
    		return 1;
    	}
    	return 0;
    }

![在这里插入图片描述][20191112140940332.png]

# 2. 组织数据 #

数据结构： 保存了学生的姓名、期中和期末考试成绩和所有家庭成绩

grade.h

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

grade.cpp

#include "grade.h"
    #include "median.h"
    
    double grade(double midterm, double final, double homework)
    { 
    	return 0.2 * midterm + 0.4 * final + 0.4 * homework;
    }
    //4-1-0
    
    
    //4-1-2
    double grade(double midterm, double final, const vector<double>& hw)
    { 
    	if (hw.size() == 0)
    	{ 
    		throw domain_error("no homework");
    	}
    	return grade(midterm, final, median(hw));
    }
    //4-1-2

median.h

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

median.cpp

#include "median.h"
    
    double median(vector<double> vec)
    { 
    	typedef vector<double>::size_type vec_sz;
    	vec_sz size = vec.size();
    	//异常对象的处理
    	if (size == 0)
    	{ 
    		throw domain_error("empty");
    	}
    	sort(vec.begin(), vec.end());
    	vec_sz mid = size / 2;
    	return size % 2 == 0 ? (vec[mid] + vec[mid - 1]) / 2 : vec[mid];
    }

Student\_info.h

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

Student\_info.cpp

#include "Student_info.h"
    
    
    bool compare(const Student_info& x, const Student_info& y)
    { 
    	return x.name < y.name;
    }
    
    istream& read(istream& is, Student_info& s)
    { 
    	// read and store the student's name and midterm and final exam grades
    	is >> s.name >> s.midterm >> s.final;
    
    	read_hw(is, s.homework);  // read and store all the student's homework grades
    	return is;
    }
    
    istream& read_hw(istream& in, vector<double>& hw)
    { 
    	if (in)
    	{ 
    		//清除之前的内容
    		hw.clear();
    		//读家庭作业
    		double x;
    		while (in >> x);
    		{ 
    			hw.push_back(x);
    		}
    		//清除流 使下一个动作对学生有效
    		in.clear();
    	}
    	return in;
    }

main.cpp

#include <algorithm>
    #include <iomanip>
    #ifndef __GNUC__
    #include <ios>
    #endif
    #include <iostream>
    #include <stdexcept>
    #include <string>
    #include <vector>
    #include "grade.h"
    #include "Student_info.h"
    
    using std::cin;                     using std::setprecision;
    using std::cout;                    using std::sort;
    using std::domain_error;            using std::streamsize;
    using std::endl;                    using std::string;
    #ifndef _MSC_VER
    using std::max;                     using std::vector;
    #else
    using std::vector;
    
    #include "../minmax.h"
    #endif
    
    int main()
    { 
    	vector<Student_info> students;
    	Student_info record;
    	string::size_type maxlen = 0;       // the length of the longest name
    
    	// read and store all the students' data.
    	// Invariant: `students' contains all the student records read so far
    	// `maxlen' contains the length of the longest name in `students'
    	while (read(cin, record)) { 
    		// find length of longest name
    		maxlen = max(maxlen, record.name.size());
    		students.push_back(record);
    	}
    
    	// alphabetize the student records
    	sort(students.begin(), students.end(), compare);
    
    	// write the names and grades
    #ifdef _MSC_VER
    	for (std::vector<Student_info>::size_type i = 0;
    #else
    	for (vector<Student_info>::size_type i = 0;
    #endif
    	     i != students.size(); ++i) { 
    
    		// write the name, padded on the right to `maxlen' `+' `1' characters
    		cout << students[i].name
    		     << string(maxlen + 1 - students[i].name.size(), ' ');
    
    		// compute and write the grade
    		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;
    }

# 待修改 #

[20191112140940332.png]: https://img-blog.csdnimg.cn/20191112140940332.png