【C++初学】课后作业汇总复习（六） 函数模板

1、函数模板

思考：如果重载的函数，其解决问题的逻辑是一致的、函数体语句相同，只是处理的数据类型不同，那么写多个相同的函数体，是重复劳动，而且还可能因为代码的冗余造成不一致性。
解决：使用模板
例：求绝对值函数的模板

主函数如下

int main()
{
int n=-5;
double d=-5.5;
cout<<abs(n)<<endl;
cout<<abs(d)<<endl;
return 0;
}

#include <iostream>
using namespace std;



template<typename T>
T abs(T x) {
    return x < 0? -x : x;
}


int main() {
    int n = -5;
    double d = -5.5;
    cout << abs(n) << endl;  // 调用 abs<int>
    cout << abs(d) << endl;  // 调用 abs<double>
    return 0;
}

2、排序函数模板

Description：
已知主函数如程序后缀代码所示，请为其编写适当的模板函数，使主函数的bubbleSort函数可以对一个整型数组和一个浮点数数组进行输入、排序、输出操作。

Sample Input：
无

Sample Output：

#include <iostream>
#include <iomanip>
using namespace std;

// 模板函数声明
template <typename T>
void bubbleSort(T arr[], int size);

//StudybarCommentBegin
int main()
{ 
   const int arraySize = 10;  // size of array
   int a[ arraySize ] = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 }, i;

   // display int array in original order
   cout << "Integer data items in original order\n";

   for ( i = 0; i < arraySize; ++i )
      cout << setw( 6 ) << a[ i ];

   bubbleSort( a, arraySize );          // sort the array

   // display int array in sorted order
   cout << "\nInteger data items in ascending order\n";

   for ( i = 0; i < arraySize; ++i )
      cout << setw( 6 ) << a[ i ];

   cout << "\n\n";

   // initialize double array
   double b[ arraySize ] = { 10.1, 9.9, 8.8, 7.7, 6.6, 5.5,
                            4.4, 3.3, 2.2, 1.1 };
   
   // display double array in original order								 
   cout << "double point data items in original order\n";

   for ( i = 0; i < arraySize; ++i )
      cout << setw( 6 ) << b[ i ];

   bubbleSort( b, arraySize );          // sort the array
   
   // display sorted double array
   cout << "\ndouble point data items in ascending order\n";

   for ( i = 0; i < arraySize; ++i )
      cout << setw( 6 ) << b[ i ];

   cout << endl;

   return 0;

} // end main
//StudybarCommentEnd

// 模板函数实现
template <typename T>
void bubbleSort(T arr[], int size) {
    for (int i = 0; i < size - 1; ++i) {
        for (int j = 0; j < size - i - 1; ++j) {
            if (arr[j] > arr[j + 1]) {
                // 交换元素
                T temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }
}

3、重载函数模板printArray

Description：
重载第七章课件10页中的printArray函数模板，代码如下：

#include

using namespace std;

// function template printArray definition

template< typename T >

void printArray( const T *arrayset, int count )

{

for ( int i = 0; i < count && arrayset[i]!=‘\0’ ; i++ )

  cout << arrayset[ i ] << " ";

cout << endl;

} // end function template printArray

int main()

{

const int aCount = 5; // size of array a

const int bCount = 7; // size of array b

const int cCount = 6; // size of array c

int a[ aCount ] = { 1, 2, 3, 4, 5 };

double b[ bCount ] = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 };

char c[ cCount ] = “HELLO”; // 6th position for null

cout << “Array a contains:” << endl;

// call integer function-template specialization

printArray( a, aCount );

cout << “Array b contains:” << endl;

// call double function-template specialization

printArray( b, bCount );

cout << “Array c contains:” << endl;

// call character function-template specialization

printArray( c, cCount );

return 0;

} // end main

重载上述函数模板，使它包含两个额外的名为 int lowSubscript （范围下限）和 int highSubscript（范围上限）的整型参数。调用这个函数会打印出数组中指定范围的元素。函数将判定lowSubscript和highSubscript是否有效，如果超出数组下标范围或highSubscript比lowSubscript小，重载的printArray函数将返回0，否则，返回打印出的元素的个数。然后修改main函数，通过三个数组a、b、c来对两个版本的printArray进行测试。

注：程序后缀代码已给出。

提示：字符’\0’是不可打印字符，因此，cout<<‘\0’; 将导致输出不确定数值。

Sample Input：
无

Sample Output：

#include <iostream>

using namespace std;

// Original function template printArray definition
template< typename T >
void printArray( const T *arrayset, int count )
{
   for ( int i = 0; i < count && arrayset[i]!='\0'; i++ )
      cout << arrayset[ i ] << " ";
   cout << endl;
} // end function template printArray

// Overloaded function template printArray with range parameters
template< typename T >
int printArray( const T *arrayset, int count, int lowSubscript, int highSubscript )
{
    // Check for invalid subscripts
    if (lowSubscript < 0 || highSubscript >= count || lowSubscript > highSubscript) {
        return 0;
    }
    
    int elementsPrinted = 0;
    for (int i = lowSubscript; i <= highSubscript; i++) {
        // For char arrays, don't print null terminators
        if (arrayset[i] != '\0') {
            cout << arrayset[i] << " ";
            elementsPrinted++;
        }
    }
    cout << endl;
    
    return elementsPrinted;
} // end overloaded function template printArray

//StudybarCommentBegin
int main()
{
    // sizes of arrays
    const int aCount = 5;
    const int bCount = 7;
    const int cCount = 6;
    
    // declare and initialize arrays
    int a[ aCount ] = { 1, 2, 3, 4, 5 };
    double b[ bCount ] = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 };
    char c[ cCount ] = "HELLO";  // 6th position for null
    int elements;
    
    // display array a using original printArray function
    cout << "\nUsing original printArray function\n";
    printArray( a, aCount );
    
    // display array a using new printArray function
    cout << "\nArray a contains:\n";
    elements = printArray( a, aCount, 0, aCount - 1 );
    cout << elements << " elements were output\n";
    
    // display elements 1-3 of array a
    cout << "Array a from 1 to 3 is:\n";
    elements = printArray( a, aCount, 1, 3 );
    cout << elements << " elements were output\n";
    
    // try to print an invalid element
    cout << "Array a output with invalid subscripts:\n";
    elements = printArray( a, aCount, -1, 10 );
    cout << elements << " elements were output\n\n";
    
    // display array b using original printArray function
    cout << "\nUsing original printArray function\n";
    printArray( a, aCount );
    
    // display array b using new printArray function
    cout << "Array b contains:\n";
    elements = printArray( b, bCount, 0, bCount - 1 );
    cout << elements << " elements were output\n";
    
    // display elements 1-3 of array b
    cout << "Array b from 1 to 3 is:\n";
    elements = printArray( b, bCount, 1, 3 );
    cout << elements << " elements were output\n";
    
    // try to print an invalid element
    cout << "Array b output with invalid subscripts:\n";
    elements = printArray( b, bCount, -1, 10 );
    cout << elements << " elements were output\n\n";
    
    // display array c using original printArray function
    cout << "\nUsing original printArray function\n";
    printArray( a, aCount );
    
    // display array c using new printArray function
    cout << "Array c contains:\n";
    elements = printArray( c, cCount, 0, cCount - 1 );
    cout << elements << " elements were output\n";
    
    // display elements 1-3 of array c
    cout << "Array c from 1 to 3 is:\n";
    elements = printArray( c, cCount, 1, 3 );
    cout << elements << " elements were output\n";
    
    // try to display an invalid element
    cout << "Array c output with invalid subscripts:\n";
    elements = printArray( c, cCount, -1, 10 );
    cout << elements << " elements were output" << endl;
    
    return 0;
    
} // end main
//StudybarCommentEnd

4、类模板

类模板的作用
使用类模板使用户可以为类声明一种模式，使得类中的某些数据成员、某些成员函数的参数、某些成员函数的返回值，能取任意类型（包括基本类型的和用户自定义类型）。

类模板的声明
类模板 template <模板参数表> class 类名 {类成员声明};
如果需要在类模板以外定义其成员函数，则要采用以下的形式： template <模板参数表> 类型名 类名<模板参数标识符列表>::函数名（参数表）
例9-2 类模板示例

#include <iostream>
#include <cstdlib>
using namespace std;
struct Student {
  int id;       //学号
  float gpa;    //平均分
}; 
template <class T>
class Store {//类模板：实现对任意类型数据进行存取
private:
    T item; // item用于存放任意类型的数据
    bool haveValue;  // haveValue标记item是否已被存入内容
public:
    Store();
    T &getElem();   //提取数据函数
    void putElem(const T &x);  //存入数据函数
};

template <class T>  
Store<T>::Store(): haveValue(false) { } 
template <class T>
T &Store<T>::getElem() {
    //如试图提取未初始化的数据，则终止程序
    if (!haveValue) {   
        cout << "No item present!" << endl;
        exit(1);    //使程序完全退出，返回到操作系统。
    }
    return item;        // 返回item中存放的数据 
}
template <class T>
void Store<T>::putElem(const T &x) {
    // 将haveValue 置为true，表示item中已存入数值   
    haveValue = true;   
    item = x;           // 将x值存入item
}

int main() {
    Store<int> s1, s2;  
    s1.putElem(3);  
    s2.putElem(-7);
    cout << s1.getElem() << "  " << s2.getElem() << endl;

    Student g = { 1000, 23 };
    Store<Student> s3;
    s3.putElem(g); 
    cout << "The student id is " << s3.getElem().id << endl;

    Store<double> d;
    cout << "Retrieving object D... ";
    cout << d.getElem() << endl;
   //d未初始化，执行函数D.getElement()时导致程序终止
    return 0;
}

5、整数集合类

实现整数集合类

要求：1、类中含两个私有变量，集合中元素的个数和集合中元素组成的数组。

        2、用Set函数输入，Show函数输出结果（按从小到大的顺序输出各个元素）。

        3、实现运算符+的重载，表示两个集合的并集。

              实现运算符&的重载，表示两个集合的交集。

              实现运算符-的重载，表示两个集合的差。

提示：1、集合中不可出现重复元素。

        2、空集时，输出empty。

样例1

输入

3

1 2 3

4

1 2 5 6

输出

1 2 3 5 6

1 2

3

样例2

输入

3

1 2 3

3

1 2 3

输出

1 2 3

1 2 3

empty

#include <iostream>
#include <algorithm>
using namespace std;

class Cassemblage {
private:
    int num;
    int elements[1000]; // Assuming a maximum size for simplicity

public:
    Cassemblage() : num(0) {}

    void Set(int arr[], int n) {
        num = 0;
        for (int i = 0; i < n; ++i) {
            bool found = false;
            for (int j = 0; j < num; ++j) {
                if (elements[j] == arr[i]) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                elements[num++] = arr[i];
            }
        }
        sort(elements, elements + num);
    }

    void Show() {
        if (num == 0) {
            cout << "empty";
        } else {
            for (int i = 0; i < num; ++i) {
                cout << elements[i];
                if (i != num - 1) {
                    cout << " ";
                }
            }
        }
    }

    Cassemblage operator+(const Cassemblage& other) const {
        Cassemblage result;
        int i = 0, j = 0;
        while (i < num && j < other.num) {
            if (elements[i] < other.elements[j]) {
                if (result.num == 0 || result.elements[result.num - 1] != elements[i]) {
                    result.elements[result.num++] = elements[i];
                }
                ++i;
            } else if (elements[i] > other.elements[j]) {
                if (result.num == 0 || result.elements[result.num - 1] != other.elements[j]) {
                    result.elements[result.num++] = other.elements[j];
                }
                ++j;
            } else {
                if (result.num == 0 || result.elements[result.num - 1] != elements[i]) {
                    result.elements[result.num++] = elements[i];
                }
                ++i;
                ++j;
            }
        }
        while (i < num) {
            if (result.num == 0 || result.elements[result.num - 1] != elements[i]) {
                result.elements[result.num++] = elements[i];
            }
            ++i;
        }
        while (j < other.num) {
            if (result.num == 0 || result.elements[result.num - 1] != other.elements[j]) {
                result.elements[result.num++] = other.elements[j];
            }
            ++j;
        }
        return result;
    }

    Cassemblage operator&(const Cassemblage& other) const {
        Cassemblage result;
        int i = 0, j = 0;
        while (i < num && j < other.num) {
            if (elements[i] < other.elements[j]) {
                ++i;
            } else if (elements[i] > other.elements[j]) {
                ++j;
            } else {
                if (result.num == 0 || result.elements[result.num - 1] != elements[i]) {
                    result.elements[result.num++] = elements[i];
                }
                ++i;
                ++j;
            }
        }
        return result;
    }

    Cassemblage operator-(const Cassemblage& other) const {
        Cassemblage result;
        int i = 0, j = 0;
        while (i < num && j < other.num) {
            if (elements[i] < other.elements[j]) {
                if (result.num == 0 || result.elements[result.num - 1] != elements[i]) {
                    result.elements[result.num++] = elements[i];
                }
                ++i;
            } else if (elements[i] > other.elements[j]) {
                ++j;
            } else {
                ++i;
                ++j;
            }
        }
        while (i < num) {
            if (result.num == 0 || result.elements[result.num - 1] != elements[i]) {
                result.elements[result.num++] = elements[i];
            }
            ++i;
        }
        return result;
    }
};

//StudybarCommentBegin
int main(int argc, char* argv[])
{
    Cassemblage z1, z2, x1, x2, x3;
    int i, n1, n2, a1[1000], a2[1000];
    
    cin >> n1;
    for(i=0; i<n1; i++)
    {
        cin >> a1[i];
    }
    z1.Set(a1, n1);

    cin >> n2;
    for(i=0; i<n2; i++)
    {
        cin >> a2[i];
    }    
    z2.Set(a2, n2);

    x1=z1+z2;
    x1.Show();
    cout << endl;

    x2=z1&z2;
    x2.Show();
    cout << endl;

    x3=z1-z2;
    x3.Show();

    return 0;
}
//StudybarCommentEnd