第6章  使用库算法

for(vector<string>::const_iterator it = bottom.begin(); it != bottom.end(); ++it)
ret.push_back(*it);</span>

ret.insert(ret.end(), bottom.begin(), bottom.end());</span>

copy(bottom.begin(), bottom.end(), back_inserter(ret));</span>

//如果参数是空白区域则为true，否则为false
bool space(char c)
{
	return isspace(c);
}

//如果参数是空白区域则为false，否则为true
bool not_space(char c)
{
	return !isspace(c);
}

vector<string> split(const string& str)
{
	typedef string::const_interator iter;
	vector<string> ret;

	iter != str.begin();
	while(i != str.end())
	{
		//忽略前端空白
		i = find_if(i, str.end(), not_space);

		//找到下一个单词的结尾
		iter j = find_if(i, str.end(), space);

		//复制在[i,j)中的字符
		if(i != str.end())
			ret.push_back(string(i,j));
		i = j;
	}
	return ret;
}</span>

// lesson6.2.cpp : 定义控制台应用程序的入口点。
//功能：判断回文
//2014.5.22

#include "stdafx.h"
#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>

using namespace std;

bool is_palindrome(const string& s)
{
  return equal(s.begin(), s.end(), s.rbegin());
}

int _tmain(int argc, _TCHAR* argv[])
{
	string s;
  while (cin >> s)
  {
    if (is_palindrome(s))
      cout << s << " is a palindrome" << endl;
    else
      cout << s << " is not a palindrome" << endl;
  }
	return 0;
}</span>

// lesson6_1.cpp : 定义控制台应用程序的入口点。
//功能：查找URL
//时间：2014.5.22

#include "stdafx.h"
#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>
#include <vector>

#include "urls.h"

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	string s;
	while (getline(cin,s))
	{
		vector<string> v = find_urls(s);
		for(vector<string>::const_iterator i = v.begin(); i != v.end(); ++i)
			cout << *i << endl;
	}
	return 0;
}
</span>

#ifndef GUARD_urls_h
#define GUARD_urls_h

#include <vector>
#include <string>

std::vector<std::string> find_urls(const std::string& s);

#endif</span>

#include <algorithm>
#include <cctype>
#include <string>
#include <vector>

#include "urls.h"

using std::find;
using std::find_if;

#ifndef _MSC_VER
using std::isalnum;
using std::isalpha;
using std::isdigit;
#endif

using std::search;
using std::string;
using std::vector;

bool not_url_char(char);

string::const_iterator
url_end(string::const_iterator, string::const_iterator);

string::const_iterator
url_beg(string::const_iterator, string::const_iterator);

vector<string> find_urls(const string& s) 
{
  vector<string> ret;
  typedef string::const_iterator iter;
  iter b = s.begin(), e = s.end();

  // 检查整个输入
  while (b != e) 
  {
    // 查找一个或多个紧跟://的字母
    b = url_beg(b, e);

    // 如果查找成功
    if (b != e) 
	{
      // 获取URL的其余部分
      iter after = url_end(b, e);

      // 记住这个URL
      ret.push_back(string(b, after));

      // 将b向前推进并查找位于本行中的其他的URL
      b = after;
    }
  }

  return ret;
}

//调用url_end目的是为了找出这个URL的结尾
string::const_iterator
url_end(string::const_iterator b, string::const_iterator e) 
{
  return find_if(b, e, not_url_char);
}

//编写这个not_url_char的谓词
bool not_url_char(char c) {
  // 除去字母数字之外，其他有可能出现在一个URL中的字符
  static const string url_ch = "~;/?:@=&$-_.+!*'(),";

  // 看c是否出现在一个URL并返回求反的结果
  return !(isalnum(c) || find(url_ch.begin(), url_ch.end(), c) != url_ch.end());

  //补充：isalnum函数是检验它的参数是否是一个字母数字字符（一个字母或者一个数字）
}

//负责识别是否有一个有效的URL,我们必须保证在://分隔符之前有一个或多个的字母，而且在它的后面至少有一个字符。
string::const_iterator
url_beg(string::const_iterator b, string::const_iterator e) 
{
  static const string sep = "://";

  typedef string::const_iterator iter;

  // `i' 标记了查找到的分隔符的位置
  iter i = b;

  while ((i = search(i, e, sep.begin(), sep.end())) != e) 
  {
      //确保分割符不是本行中唯一的一个符号
    if (i != b && i + sep.size() != e)
	{

      // `beg标记协议名称的开关
      iter beg = i;
      while (beg != b && isalpha(beg[-1])) //isalpha 判断不是字母
	   --beg;

      // 在分隔符前面以及后面至少有一个字符吗？
      if (beg != i && !not_url_char(i[sep.size()]))
	return beg;
    }

    //我们找到的分隔符不是一个URL的一部分
	if(i != e)
    i += sep.size();
  }

  return e;
}</span>

// lesson6_3.cpp : 定义控制台应用程序的入口点。
//功能：计算成绩
//时间：2014.5.22

#include "stdafx.h"
#include <vector>
#include <iostream>

#include "analysis.h"
#include "Student_info.h"

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	//做以及没做家庭作业的学生
	vector<Student_info> did,didnt;

	//读入学生记录并划分他们
	Student_info student;
	while(read(cin,student))
	{
		if(did_all_hw(student))
			did.push_back(student);
		else
			didnt.push_back(student);
	}

	//证实这些分析将向我们出示某些结果
	if(did.empty())
	{
		cout << "No student did all the homework!" << endl;
		return 1;
	}
	if(didnt.empty())
	{
		cout << "Every student did all the homework!" << endl;
		return 1;
	}

	//进行分析
	write_analysis(cout, "median", median_analysis, did, didnt);
	write_analysis(cout, "average", average_analysis, did, didnt);
	write_analysis(cout, "median of homework turned in", optimistic_median_analysis, did, didnt);

	return 0;
}</span>

#include <algorithm>

#include "Student_info.h"

using namespace std;

//函数的目的就是查找储存在里面的所有值中是否有为0的
bool did_all_hw(const Student_info& s)
{
	return((find(s.homework.begin(), s.homework.end(), 0)) == s.homework.end());
}</span>

//功能：分析
//时间：2014.5.22
#include <slgorithm>
#include <iostream>
#include <iterator>
#include <numeric>
#include <stdexcept>
#include <vector>

#include "Student_info.h"
#include "grade.h"
#include "median.h"

using namespace std;

//建立一个辅助函数在grade内执行try语句并且处理异常
double grade_aux(const Student_info& s)
{
	try
	{
		return grade(s);
	}
	catch(domain_error)
	{
		return grade(s.midterm, s.final, 0)
	}
}
//median_analysis
double median_analysis(const vector<Student_info>& students) 
{
  vector<double> grades;

  transform(students.begin(), students.end(),back_inserter(grades), grade_aux);

  return median(grades);
}

//使用一个分析例程来比较两个学生数据的集合
void write_analysis(ostream& out, const string& name, double analysis(const vector<Student_info>&), const vector<Student_info>& did, const vector<Student_info>& didnt)
{
	out << name << ": median(did) = " << analysis(did) << ",median(didnt) = " << analysis(didnt) << endl;
}

//计算家庭作业的平均成绩
double average(const vector<double>& v)
{
	return accumulate(v.begin(), v.end(), 0.0) / v.size();  //这里一定要注意用0.0这样求出的值才不会丢了小数点部分
}

//计算总成绩
double average_grade(const Student_info& s)
{
	return grade(s.midterm, s.final, average(s.homework));
}

//平均函数分析
double average_analysis(const vector<Student_info>& students)
{
	vector<double> grades;

	transform(students.begin(), students.end(), back_inserter(grades), average_grade);

	return median(grades);
}

//上交家庭作业的中值,s.homework的非零元素的中值，如果没有这样的元素存在的话，则为0
double optimistic_median(const Student_info& s)
{
	vector<double> nonzero;
	remove_copy(s.homework.begin(), s.homework.end(), back_inserter(nonzero),0);

	if(nonzero.empty())
		return grade(s.midterm, s.final, 0);
	else
		return grade(s.midterm, s.final, median(nonzero));
}

//optimistic_median_analysis
double optimistic_median_analysis(const vector<Student_info>& students)
{
	vector<double> grades;

	transform(students.begin(),students.end(), back_inserter(grades), optimistic_median);

	return median(grades);
}
</span>

#include <algorithm>
#include <iterator>
#include <vector>

#include "Student_info.h"
#include "grade.h"

using namespace std;

vector<Student_info> extract_fails(vector<Student_info>& students)
{
	vector<Student_info> fail;
	remove_copy_if(students.begin(), students.end(),back_inserter(fail),pgrade);

	students.erase(remove_if(students.begin(),students.end(), fgrade)， students.end());

	return fail;
}</span>

#include <algorithm>
#include <vector>

#include "Student_info.h"
#include "grade.h"

using std::stable_partition;
using std::vector;

vector<Student_info> extract_fails(vector<Student_info>& students)
{
   vector<Student_info>::iterator iter = stable_partition(students.begin(), students.end(), pgrade);
   vector<Student_info> fail(iter, students.end());
   students.erase(iter, students.end());

   return fail;
}</span>