偏好標準庫解決方案而非手動編寫的模仿者

#include "stdafx.h"
#include <deque>
#include <iostream>
#include <algorithm>

void countExample()
{
    int myArray[10] = { 1, 2, 1, 3, 1, 4, 1, 5, 1, 6 };
    std::cout << "myArray contains " << std::count(myArray, myArray + 10, 1) << " 1s" << std::endl;

    std::deque<int> myDeque(myArray, myArray + 10);
    std::cout << "myDeque contains " << std::count(myDeque.begin(), myDeque.end(), 1) << " 1s" << std::endl;
}
void incorrectCustomCounter()
{
    int myArray[10] = { 1, 2, 1, 3, 1, 4, 1, 5, 1, 6 };

    // Manually search for 1s in the deque.  Can you spot the errors in the loop?
    int count(0);
    for(int i = 1; i <= 10; ++i)
    {
        if(myArray<i> = 1)
        {
            ++count;
        }
    }
    std::cout << "myDeque contains " << count << " 1s" << std::endl;
}
int main()
{
    countExample();
    incorrectCustomCounter();
    return 0;
}

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

class Student
{
public:
    //constructors
    Student(std::string firstName, std::string lastName, std::string hometown, unsigned int id) 
        : firstName_(firstName), lastName_(lastName), hometown_(hometown), id_(id)  {}
    Student() : firstName_(""), lastName_(""), hometown_(""), id_(0) {}

    //destructor
    ~Student() {}

    // accessor functions
    std::string getHometown() const { return hometown_; }
    std::string getFirstName() const { return firstName_; }
    std::string getLastName() const { return lastName_; }
    unsigned int getId() const { return id_; };

    // mutator functions.
    void addSubject(const std::string& subject) { classes_.push_back(subject); }
    void setFirstName(std::string& name) { firstName_ = name; }
    void setlastName(std::string& name) { lastName_ = name; }
    void setHometown(std::string& name) { hometown_ = name; }
    void setId(std::string& name) { firstName_ = name; }

    // overloaded << so that we can output directly to a stream
    friend std::ostream& operator<<(std::ostream& os, const Student& s)
    {
        return os << s.getFirstName() << "\t\t" << s.getLastName() << "\t\t" 
                  << s.getHometown() << "\t" << s.getId(); 
    }

    // This is an overloaded relational operator.  It is needed to allow arrays of 
    // Student objects to be sorted using std::sort.  This is called during the
    // operation so that each object in the array can be compared against one another.
    bool operator<(const Student& rhs)
    {
        return (id_ < rhs.id_);
    }

    // declare friends
    friend struct PrintSubjects;
    friend struct IsTakingCalculus;

private:
    std::string firstName_;
    std::string lastName_;
    std::string hometown_;
    unsigned int id_;
    std::deque<std::string> classes_;

};


    // printing functor for use with std::foreach.  It works because operator<< is overloaded
    // for the student class.  
    struct SendToStream 
    {
        void operator() (const Student& s) { std::cout << s << std::endl; }
    } StsFtr;

    struct PrintSubjects 
    {
        void operator() (const Student& s) 
        { 
            std::cout << "\n" << s << "\n";
            std::deque<std::string>::const_iterator pos = s.classes_.begin();
            for(; pos < s.classes_.end(); ++pos)
            {
                std::cout << *pos << "   ";  // 3 spaces
            }
            std::cout << "\n";
        }
    } PsFtr;


    // used with count_if to count the number of students from san diego.  
    struct IsFromSanDiego 
    {
        bool operator() (const Student& s) { return (s.getHometown() == "San Diego, CA"); }
    } IfSdFtr;

    // used with count_if to count the number of students taking calculus
    struct IsTakingCalculus 
    {
        bool operator() (const Student& s) 
        { 
            return (std::find(s.classes_.begin(), s.classes_.end(), "calculus") != s.classes_.end()); 
        }
    } ItcFtr;

typedef std::deque<Student> Students;

int main()
{
    //Build an array of students.
    Students theStudents;

    // construct 10 students
    theStudents.push_back(Student("Sandra", "Fox", "San Diego, CA", 12111));
    theStudents.push_back(Student("Warren", "Pierce", "Fairbanks, AK", 12112));
    theStudents.push_back(Student("Dan", "Wright", "St. Louis, MO", 12113));
    theStudents.push_back(Student("Amelia", "Timlin", "Erie, PA", 24312));
    theStudents.push_back(Student("Anne", "Bradley", "Boston, MA", 24315));
    theStudents.push_back(Student("Mike", "Harding", "San Diego, CA", 24316));
    theStudents.push_back(Student("Sandra", "Brown", "Boston, MA", 38125));
    theStudents.push_back(Student("Melissa", "Turner", "Boston, MA", 38126));
    theStudents.push_back(Student("Jack", "Turner", "San Diego, CA", 12114));
    theStudents.push_back(Student("Sandra", "Rice", "St. Louis, MO", 24317));

    // print students in the original order
    std::cout << "\nPrint the students in the original order. " << std::endl;
    std::for_each(theStudents.begin(), theStudents.end(), StsFtr);

    // Use std algorithms to collect and display student metrics.
    Students::iterator pos;

    // print the student with the largest student id
    std::cout << "\nPrint the student with the largest id. " << std::endl;
    if( (pos = std::max_element(theStudents.begin(), theStudents.end())) != theStudents.end())
        StsFtr(*pos);

    // print the student with the smallest student id
    std::cout << "\nPrint the student with the smallest id. " << std::endl;
    if( (pos = std::min_element(theStudents.begin(), theStudents.end())) != theStudents.end())
        StsFtr(*pos);

    // sort the students by student id.  The operator< for the student uses the id so
    // we don't need to use a functor.
    std::cout << "\nSort the student by their student id. " << std::endl;
    std::sort(theStudents.begin(), theStudents.end());
    std::for_each(theStudents.begin(), theStudents.end(), StsFtr);

    // reverse the order
    std::cout << "\nReverse the order of elements within the container" << std::endl;
    std::reverse(theStudents.begin(), theStudents.end());
    std::for_each(theStudents.begin(), theStudents.end(), StsFtr);

    // shuffle the array into a random order
    std::cout << "\nShuffle the container " << std::endl;
    std::random_shuffle(theStudents.begin(), theStudents.end());
    std::for_each(theStudents.begin(), theStudents.end(), StsFtr);

    // add some subjects to the student classes
    std::string subjectsArray[7] = { "calculus", "physics", "philosophy", "history", "biology", "grammar", "spanish" };
    for(pos = theStudents.begin(); pos < theStudents.end(); ++pos)
    {
        // add three random subjects to each student object
        pos->addSubject(subjectsArray[1]);
        pos->addSubject(subjectsArray[3]);
        pos->addSubject(subjectsArray[5]);
        std::random_shuffle(subjectsArray, subjectsArray + 5);
    }
    std::for_each(theStudents.begin(), theStudents.end(), PsFtr);

    // Try using find and count functions using a predicate that searches for subjects contained 
    // in student objects.
    std::cout << std::count_if(theStudents.begin(), theStudents.end(), ItcFtr)
              << " are taking calculus.\n";

    std::cout << std::count_if(theStudents.begin(), theStudents.end(), IfSdFtr)
              << " are from San Diego, CA.\n";
    return 0;
}