《C++ Primer Plus（第6版）》编程练习代码 Chapter 8

Chapter 8

8.1

#include<iostream>using namespace std;void show(char * ch, int n = 0);int main(){    char ch[10] = "A B C\n";    for (int i = 0; i < 5; ++i)    {        cout << i << endl;        show(ch, i);    }    cin.get();    cin.get();}void show(char * ch, int n){    static int count = 0;    int lim = ++count;    if (n == 0)        lim = 1;    for (int i = 0; i < lim; ++i)    {        cout << ch;    }}

重要知识点：static的用法，在这里可以在函数内部实现记录函数调用的次数。

8.2

#include<iostream>using namespace std;const int SIZE = 30;struct CandyBar{    char name[SIZE];    double weight;    int heat;};void fill(CandyBar & c, const char * name = "Millennium Munch", const double weight = 2.85, const int heat = 350);void Show(const CandyBar & c);int main(){    CandyBar candy = {"void", 0.0, 0};    fill(candy);    Show(candy);    cin.get();    cin.get();}void fill(CandyBar & c, const char * name, const double weight, const int heat){    int i = 0;    while (name[i])    {        c.name[i] = name[i];        ++i;    }    while (i < SIZE)    {        c.name[i] = '\0';        ++i;    }    c.weight = weight;    c.heat = heat;}void Show(const CandyBar & c){    cout << "name of CandyBar: " << c.name << endl;    cout << "weight of CandyBar: " << c.weight << endl;    cout << "heat of CandyBar: " << c.heat << endl;}

重要知识点：①. 函数默认值必须从右向左设置; ②. 可以直接输入数据源类型作为函数引用类型, 比如这里candy作为 candy &输入.

8.3

#include<iostream>#include<cctype>#include<string>using namespace std;void L2U(string & str);int main(){    string str, q = "q";    cout << "Enter a string (qto quit): ";    getline(cin, str);    while (str != q)    {        L2U(str);        cout << str << endl;        cout << "Next string (q to quit): ";        getline(cin, str);    }    cout << "Bye.";    cin.get();    cin.get();}void L2U(string & str){    int n = str.length();    for (int i = 0; i < n; ++i)    {        str[i] = toupper(str[i]);    }}

重要知识点: ①. getline(cin, str) 读取整行字符; ②. string.length()返回string长度; ③. toupper( )只能接受单个字符.

8.4

#include<iostream>#include<cstring>using namespace std;struct stringy{    char * str;    int ct;};void set(stringy & stri, const char * ch);void show(const stringy stri, const int n = 1);void show(const char * ch, int n = 1);int main(){    stringy beany;    char testing[] = "Reality isn't  what it used to be.";    set(beany, testing);    show(beany);    show(beany, 2);    testing[0] = 'D';    testing[1] = 'u';    show(testing);    show(testing, 3);    show("Done!");    cin.get();    cin.get();    return 0;}void set(stringy & stri, const char * ch){    int len = strlen(ch);    char * st = new char[len + 1];    stri.str = st;    strcpy_s(st, len + 1, ch);    stri.ct = len;}void show(const stringy stri, const int n){    for (int i = 0; i < n; ++i)        cout << stri.str << endl;}void show(const char * ch, int n){    for (int i = 0; i < n; ++i)        cout << ch << endl;}

重要知识点: ①. 需要用变量设置字符串长度时, 需要用new : char * st = new char[len + 1], 设置st指向一个长度为len+1(包含’\0’)的字符串开头; ②. 使用strcpy会报错,应当使用更为安全的strcpy_s: strcpy(st, len + 1, ch) 即把ch中(len+1)个字符复制到st中.

8.5

#include<iostream>using namespace std;template<class T> T max5(T a[]);int main(){    int a1[5] = { 1, 2, 3, 4, 5 };    double a2[5] = { 1.1, 2.2, 3.5, 4.3, 5.9 };    cout << "Max of a1: " << max5(a1) << endl;    cout << "Max of a2: " << max5(a2);    cin.get();}template<class T> T max5(T a[]){    T max = a[0];    for (int i = 1; i < 5; ++i)    {        if (a[i] > max)            max = a[i];    }    return max;}

重要知识点: ①. 模板函数 template <class T> 的使用: template<class T> T max5(T a[]).

8.6

#include<iostream>#include<cstring>using namespace std;template<class T> T maxn(T a[], int n);template<> char * maxn<char *>(char * a[], int n);int main(){    const int intN = 6, doubleN = 4, charN = 5;    int a[intN] = { 2,3,1,4,5,6 };    double b[doubleN] = { 1.3, 2.5, 6.4, 5.1 };    char * c[charN] = { "hello", "yo", "homme", "nice to meet you", "how are you?" };    cout << "Max of int: " << maxn(a, intN) << endl;    cout << "Max of double: " << maxn(b, doubleN) << endl;    cout << "Max of char: " << maxn(c, charN) << endl;    cin.get();}template<class T> T maxn(T a[], int n){    T max = a[0];    for (int i = 0; i < n; ++i)    {        if (a[i] > max)            max = a[i];    }    return max;}template<> char * maxn<char *>(char * a[], int n){    int * len = new int[n];    int max = 0;    char * ind = a[0];    for (int i = 0; i < n; ++i)    {        len[i] = strlen(a[i]);        if (len[i] > max)        {            max = len[i];            ind = a[i];        }    }    delete[] len;    return ind;}

重要知识点: ①. 模板函数具体化 template<> char * maxn<char *>(char * a[], int n); ②. 函数调用字符串组: char * a[k] 代表k个(k行)字符串的指针组成的指针数组, a[k] == (a + k) ; 对比函数调用二维数组: int ar[][k], 代表k列数组的指针, ar[][k] == (*ar)[k], ar[m][n] = (*(ar + m) + n) ,其中ar为指向第一行第一列数字的指针.

8.7

#include<iostream>using namespace std;template<typename T> void SumArray(T arr[], int n);template<typename T> void SumArray(T * arr[], int n);struct debts{    char name[50];    double amount;};int main(){    int things[6] = { 13, 31, 103, 301, 310, 130 };    struct debts mr_E[3] =    {        {"Ima Wolfe", 2400.0},        {"Ura Foxe", 1300.0},        {"Iby Stout", 1800.0}    };    double * pd[3];    for (int i = 0; i < 3; i++)        pd[i] = &mr_E[i].amount;    cout << "Listing Mr. E's sum of things:\n";    SumArray(things, 6);    cout << "Listing Me. E's debts:\n";    SumArray(pd, 3);    cin.get();    cin.get();}template<typename T>void SumArray(T arr[], int n){    cout << "template A\n";    int sum = 0;    for (int i = 0; i < n; ++i)        sum += arr[i];    cout << sum << endl;}template<typename T>void SumArray(T * arr[], int n){    double sum = 0;    cout << "template B\n";    for (int i = 0; i < n; ++i)        sum += *arr[i];    cout << sum << endl;}

重点知识点: ①. 重载解析选择顺序为: 完全匹配(常规函数由于模板) > 提升转换(如char/short转化为int,float转化为double) > 标准转换(如int转换为char, long转换为double) > 用户定义的转换(如类声明中的定义).