<span style="font-family:KaiTi_GB2312;">//根据学生的期中考试、期末考试、家庭作业成绩来计算总成绩
double grade(double midterm, double final, double homework)
{
return 0.2 * midterm + 0.4 * final + 0.4 * homework;
}</span><span style="font-family:KaiTi_GB2312;">/计算一个vector<double>类型的变量的中值
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];
}</span><span style="font-family:KaiTi_GB2312;">//根据期中、期末考试成绩和保存家庭作业的向量来计算学生的总成绩
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));
}</span><span style="font-family:KaiTi_GB2312;">//从输入流中将家庭作业的成绩读入一个vector<double>中
istream read_hw(istream& in, vector<double>& hw)
{
if(in)
{
//清除原先的内容
hw.clear();
//读家庭作业成绩
double x;
while (in >> x)
hw.push_back(x);
//清除流以使输入动作对下一个学生有效
in.clear();
}
return in;
}</span><span style="font-family:KaiTi_GB2312;">// lesson4_1.cpp : 定义控制台应用程序的入口点。
//功能：使用函数来计算学生的成绩
//时间：2014.5.12
#include "stdafx.h"
#include <algorithm>
#include <iomanip>
//#include <ios>
#include <stdexcept>
#include <iostream>
#include <string>
#include <vector>
using std::cin;
using std::cout;
using std::domain_error;
using std::endl;
using std::istream;
using std::ostream;
using std::setprecision;
using std::sort;
using std::streamsize;
using std::string;
using std::vector;
//根据学生的期中考试、期末考试、家庭作业成绩来计算总成绩
double grade(double midterm, double final, double homework)
{
return 0.2 * midterm + 0.4 * final + 0.4 * homework;
}
//计算一个vector<double>类型的变量的中值
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];
}
//根据期中、期末考试成绩和保存家庭作业的向量来计算学生的总成绩
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));
}
//从输入流中将家庭作业的成绩读入一个vector<double>中
istream& read_hw(istream& in, vector<double>& hw)
{
if(in)
{
//清除原先的内容
hw.clear();
//读家庭作业成绩
double x;
while (in >> x)
hw.push_back(x);
//清除流以使输入动作对下一个学生有效
in.clear();
}
return in;
}
int _tmain(int argc, _TCHAR* argv[])
{
//请求并读入学生姓名
cout << "Please enter your first name: ";
string name;
cin >> name;
cout << "Hello, " << name << "!" << endl;
//请求并读入期中和期末考试的成绩
cout << "Please enter your midterm and final exam grades: ";
double midterm, final;
cin >> midterm >> final;
//请求用户输入家庭作业成绩
cout << "Enter all your homework grades, "
"followed by end-of-file: ";
vector<double> homework;
//读入家庭作业成绩
read_hw(cin, homework);
//如果可以的话，计算生成总成绩
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 your grades. "
<< "Please try again." << endl;
return 1;
}
return 0;
}
</span>
<span style="font-family:KaiTi_GB2312;">struct Student_info
{
string name;
double midterm, final;
vector<double> homework;
};//这里一定要注意分号是不可缺少的</span><span style="font-family:KaiTi_GB2312;">//需要读学生的姓名以及考试成绩
istream& read(istream& is, Student_info& s)
{
is >> s.name >> s.midterm >> s.final;
read_hw(is, s.homework);//读入并储存学生的所有家庭作业成绩
return is;
}</span><span style="font-family:KaiTi_GB2312;">double grade(const Student_info& s)
{
return grade(s.midterm, s.fianl, s.homework);
}</span><span style="font-family:KaiTi_GB2312;">sort(student.begin(), student.end());</span>
<span style="font-family:KaiTi_GB2312;">// 按字母顺序排列学生记录
bool compare(const Student_info& x, const Studnt_info& y)
{
return x.name < y.name;
}
sort(students.begin(), students.end(), compare);</span><span style="font-family:KaiTi_GB2312;">int _tmain(int argc, _TCHAR* argv[])
{
vector<Student_info> students;
Student_info record;
string::size_type maxlen = 0; //最长的姓名的长度
//读入并存储所有学生的数据
//不变式
// students 包含了所有的学生的记录
// max包含了students中最长的姓名
while (read(cin, record))
//找出最长的姓名的长度
{
maxlen = max(maxlen, record.name.size());
students.push_back(record);
}
// 按字母顺序排列学生记录
sort(students.begin(), students.end(), compare);
//输出姓名和成绩
for (std::vector<Student_info>::size_type i = 0; j != students.size(); ++i)
{
//输出姓名，把姓名填充至maxlen + 1 个字符长度
cout << setw(maxlen+1) << students[i].name;
//计算并输出成绩
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;
}</span><span style="font-family:KaiTi_GB2312;">//median函数的源文件
#include "stdafx.h"
#include <algorithm> //获取sort声明
#include <stdexcept> //获取domain_error的声明
#include <vector> //获取vector的声明
using namespace std;
//计算一个vector<double>类型的对象的中值
{
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];
}</span><span style="font-family:KaiTi_GB2312;">//使用median函数的一种较好的方法
#include "median.h"
#include <vector>
int main
{……}</span><span style="font-family:KaiTi_GB2312;">#ifndef GUARD_median_h #define GUARD_median_h #include <vector> double median(vector<double>); #endif</span>
<span style="font-family:KaiTi_GB2312;">#ifndef GUARD_Student_info
#define GUARD_Student_info
//Student_info.h 头文件
#include <iostream>
#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(std::istream&, std::vector<double>&);
#endif </span><span style="font-family:KaiTi_GB2312;">#include "Student_info.h"
using std::istream;
using std::vector;
bool compare(const Student_info& x, const Student_info& y)
{
return x.name < y.name;
}
istream& read(istream& is, Student_info& s)
{
//读和储存学生的名字,期中和期末考试成绩
is >> s.name >> s.midterm >> s.final;
read_hw(is, s.homework); //读和储存家庭作业成绩
return is;
}
//读一个家庭作业分数，储存在一个'vector<double>'向量中
istream& read_hw(istream& in, vector<double>& hw)
{
if(in)
{
//清除先前的内容
hw.clear();
//读家庭作业分数
double x;
while (in >> x)
hw.push_back(x);
//清除the stream 保证可以工作到下一个学生
in.clear();
}
return in;
}</span><span style="font-family:KaiTi_GB2312;">#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&); double grade(const Student_info&); #endif</span>
<span style="font-family:KaiTi_GB2312;">#include <stdexcept>
#include <vector>
#include "grade.h"
#include "median.h"
#include "Student_info.h"
using std::domain_error; using std::vector;
//计算一个vector<double>类型的对象的中值
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];
}
//根据期中、期末考试成绩和保存家庭作业的向量来计算学生的总成绩
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));
}
//需要读学生的姓名以及考试成绩
istream& read(istream& is, Student_info& s)
{
is >> s.name >> s.midterm >> s.final;
read_hw(is, s.homework);//读入并储存学生的所有家庭作业成绩
return is;
}</span><span style="font-family:KaiTi_GB2312;">// lesson4.2.cpp : 定义控制台应用程序的入口点。
//功能：修正后的计算成绩的程序
//时间：2014.5.12
#include "stdafx.h"
#include <algorithm>
#include <iomanip>
#include <stdexcept>
#include <string>
#include <vector>
#include "grade.h"
#include "Student_info.h"
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
vector<Student_info> students;
Student_info record;
string::size_type maxlen = 0; //最长的姓名的长度
//读入并存储所有学生的数据
//不变式
// students 包含了所有的学生的记录
// max包含了students中最长的姓名
while (read(cin, record))
//找出最长的姓名的长度
{
maxlen = max(maxlen, record.name.size());
students.push_back(record);
}
// 按字母顺序排列学生记录
sort(students.begin(), students.end(), compare);
//输出姓名和成绩
for (std::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 << setw(maxlen+1) << students[i].name;
//计算并输出成绩
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;
}
</span><span style="font-family:KaiTi_GB2312;">// lesson4_3.cpp : 定义控制台应用程序的入口点。
//功能：编写一个程序来计算从1-100的整数(int)值的平方。程序的输出分为两列；第一列是整数值。第二列是整数值的平方
//时间：2014.5.12
#include "stdafx.h"
#include <cmath>
#include <iomanip> //定义控制器setprecision 这个控制器可以让我们指明输出所包含的有效位数
#include <iostream>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
for(int i = 1; i <= 100; ++i)
{
cout << setw(3)
<< i
<< setw(6)
<< i * i
<< endl;
}
return 0;
}
</span>运行结果：
<span style="font-family:KaiTi_GB2312;">// lesson4_4.cpp : 定义控制台应用程序的入口点。
//功能：让它更好的适应性，当i增长的时不需要修正setw的参数
//时间：2014.5.12
#include "stdafx.h"
#include <cmath>
#include <iomanip>
#include <iostream>
using namespace std;
int get_width(double n)
{
return log10(n) + 1;
}
int _tmain(int argc, _TCHAR* argv[])
{
double max = 100.0;
for(int i = 1; i <= max; ++i)
{
cout << setw(get_width(max))
<< i
<< setw(get_width(max * max) + 1)
<< i * i
<< endl;
}
return 0;
}
</span><span style="font-family:KaiTi_GB2312;">// lesson4_5.cpp : 定义控制台应用程序的入口点。
//功能：编写一个函数来从输入流读单词，把读到的单词存储在一个向量中，利用这个函数编写一个程序来计算输入的单词的数目以及每一个单词所出现的次数。
//时间：2014.5.13
#include "stdafx.h"
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
//从输入流中将单词读入到一个vector<string>
istream& read_words(istream& in, vector<string>& words)
{
if(in)
{
//清除原先的内容
words.clear();
//读单词
string word;
while (in >> word)
words.push_back(word);
//清除流以使输入动作对下一个单词有效
in.clear();
}
return in;
}
int _tmain(int argc, _TCHAR* argv[])
{
typedef vector<string>::size_type vec_sz;
vector<string> words;
read_words(cin, words);
cout << "Num of words: " << words.size() << endl;
sort(words.begin(), words.end());
string prev_word = "";
int count = 0;
for(vec_sz i = 0;i < words.size(); ++i)
{
if (words[i] != prev_word)
{
if (prev_word != "")
{
cout << prev_word << " appeared " << count << "times" << endl;
}
prev_word = words[i];
count = 1;
}
else
++count;
}
cout << prev_word << " appeared " << count << "times" << endl;
return 0;
}
</span>
这个语句的后面空白部分，都删除掉，免得有不可见的全角空格。可能是不小心按到空格键了。
9、编写一个程序来计算存储在一个vector<double>类型的向量中的数据的平均值<span style="font-family:KaiTi_GB2312;">// lesson4_7.cpp : 定义控制台应用程序的入口点。
//功能：编写一个程序来计算存储在一个vector<double>类型的向量中的数据的平均值
#include "stdafx.h"
#include <iostream>
#include <numeric>
#include <vector>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
vector<double> nums;
double num;
while (cin >> num)
nums.push_back(num);
cout << accumulate(nums.begin(), nums.end(), 0.0) / nums.size() << endl;
//如果不要求存储在一个vector<double>类型的向量
/*int count = 0;
double sum = 0;
double x; //把数据读入变量x中
while (cin >> x)
{
++count;
sum += x;
}
cout << "The avg: " << sum / count << endl;
*/
return 0;
}
</span>Accelerated C++学习笔记5—<组织程序和数据>,布布扣,bubuko.com
Accelerated C++学习笔记5—<组织程序和数据>
原文：http://blog.csdn.net/to_xidianhph_youth/article/details/26366653