编程环境Visual Studio 2017
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#include <iostream> #include <string> #include <cctype> #include <cstring> using namespace std; // practice 1 void fun_of_p8_1(char *str, int print_times = 0) { // 这里也将print_times也打印出来，方便演示 cout << "String: " << str << " , print_times: " << print_times << endl; if (print_times > 1) { print_times--; fun_of_p8_1(str, print_times); } return; } void p8_1(void) { char str[128]; int print_times = 0; cout << "Enter the string you want to print: "; cin.getline(str, 128); cout << "Enter the times you want to print: "; cin >> print_times; // 测试传入两个参数 cout << "Test fun which has two prematers: " << endl; fun_of_p8_1(str, print_times); // 测试传入一个参数 cout << "Test fun which has one premater: " << endl; fun_of_p8_1(str); } // practice 2 struct CandyBar { char company[128]; double weight; int heat; }; void print_CandyBar(const struct CandyBar &candybar) { cout << "CandyBar company: " << candybar.company << endl; cout << "CandyBar weight: " << candybar.weight << endl; cout << "CandyBar heat: " << candybar.heat << endl; } void fill_CandyBar(struct CandyBar &candybar, char *company, double weight, int heat) { /* 如果使用strcpy遇到如下错误： error C4996: 'strcpy': This function or variable may be unsafe. Consider using strcpy_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. 1>c:\program files (x86)\windows kits\10\include\10.0.15063.0\ucrt\string.h(136): note: 参见“strcpy”的声明 可以这样子解决：右键工程名-->属性-->C/C++-->预处理器-->预处理器定义，编辑右边输入框加入：_CRT_SECURE_NO_WARNINGS */ strcpy(candybar.company, company); candybar.weight = weight; candybar.heat = heat; } void p8_2(void) { struct CandyBar candybar = { "" }; char company[128]; double weight = 0.0; int heat = 0; cout << "Enter the company of candybar: "; cin.getline(company, 128); cout << "Enter the weight of candybar: "; cin >> weight; cout << "Enter the heat of candybar: "; cin >> heat; fill_CandyBar(candybar, company, weight, heat); print_CandyBar(candybar); return; } // practice 3 void p8_3(void) { string input; cout << "Enter a string (q to quit): "; getline(cin, input); while (input[0] != 'q') { for (size_t i = 0; i < input.length(); i++) { input[i] = toupper(input[i]); } cout << input << endl; cout << "Next string (q to quit): "; getline(cin, input); } } // practice 4 struct stringy { char *str; int ct; }; void set(struct stringy &in_stringy, char * in_string) { int string_length = strlen(in_string); in_stringy.str = new char(string_length + 1); strcpy(in_stringy.str, in_string); in_stringy.ct = string_length; } void show(const struct stringy &in_stringy, int print_times = 1) { for (int i = 0; i < print_times; i++) { cout << "member string of struct stringy: " << in_stringy.str << endl; } } void show(const char * str, int print_times = 1) { for (int i = 0; i < print_times; i++) { cout << "Print char string: " << str << endl; } } int p8_4(void) { 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!"); return 0; } // practice 5 template <typename T> T max5(T in_array[]) { T max = in_array[0]; for (size_t i = 0; i < 5; i++) { if (max < in_array[i]) { max = in_array[i]; } } return max; } void p8_5(void) { int int_array[5] = {32, 43, 66, 23, 54}; double double_array[5] = { 32.4, 33.3, 61.3, 646.3, 23.5 }; int int_array_max = max5(int_array); double double_array_max = max5(double_array); cout << "max of int array: " << int_array_max << endl; cout << "max of double array: " << double_array_max << endl; } // practice 6 template <typename T> T maxn(T in_array[], int array_size) { T max = in_array[0]; for (int i = 0; i < array_size; i++) { if (max < in_array[i]) { max = in_array[i]; } } return max; } // 显示具体化 template <> const char * maxn(const char *in_str[], int n) { const char * str = in_str[0]; for (int i = 0; i < n; i++) { if (strlen(str) < strlen(in_str[i])) { str = in_str[i]; } } return str; } void p8_6(void) { int int_array[6] = { 43, 235, 54, 232, 123, 65 }; double double_array[4] = { 32.1, 453.2, 53.3, 67.4 }; const char * str_array[5] = { "Hello Jimmy!", "Hello World!", "ABCDEFG,HIJKLMN", "Today is a goood day!", "C++ Primer Plus!" }; int int_max = maxn(int_array, 6); double double_max = maxn(double_array, 4); const char * length_max_str = maxn(str_array, 5); cout << "max of int array: " << int_max << endl; cout << "max of double array: " << double_max << endl; cout << "max length string of string array: " << length_max_str << endl; } // practice 7 template <typename T> T SumArray(T arr[], int n); template <typename T> T SumArray(T * arr[], int n); struct debts { char name[50]; double amount; }; int p8_7(void) { int thing[6] = { 13, 31, 103, 301, 310, 130 }; int int_sum = 0; struct debts mr_E[3] = { {"Ima Wolfe", 2400.0}, {"Ura Foxe", 1300.0}, {"Iby Stout", 1800.0} }; double *pd[3]; double double_sum = 0.0; for (size_t i = 0; i < 3; i++) { pd[i] = &mr_E[i].amount; } int_sum = SumArray(thing, 6); double_sum = SumArray(pd, 3); cout << "Sum of int array: " << int_sum << endl; cout << "Sum of double* array: " << double_sum << endl; return 0; } template <typename T> T SumArray(T arr[], int n) { // 下面的sum初始化，在便宜的时候会有warning提示，有个简单的方法可以解决，那就是将sum初始化为arr的第一个元素，然后for循环从i=1开始 T sum = 0.0; for (int i = 0; i < n; i++) { sum += arr[i]; } return sum; } template <typename T> T SumArray(T * arr[], int n) { T sum = 0.0; for (int i = 0; i < n; i++) { sum += *(arr[i]); } return sum; } // main int main(int argc, char **argv) { p8_7(); while (cin.get()); } |
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第六题有问题，char* 编译器不通过 const char*可以
谢谢告知，已修改
第一题有问题，应为print_times > 0，因为题目要求第二个参数不为0时，打印字符串的次数要为函数被调用的次数，而非第二个参数的值
书不在身边，所以没办法确认。不过按照你这样说的话，print_times>1没有错啊，print_times=1的时候就调用fun_of_p8_1一次，print_times=2就调用两次......以此类推
不是啊，你这样是利用迭代实现了打印指定次数，而不是打印函数调用次数。
附上题目：
1．编写通常接受一个参数（字符串的地址），并打印该字符串的函数。然而，如果提供了第二个参数（int类型），且该参数不为0，则该函数打印字符串的次数将为该函数被调用的次数（注意，字符串的打印次数不等于第二个参数的值，而等于函数被调用的次数）。是的，这是一个非常可笑的函数，但它让您能够使用本章介绍的一些技术。在一个简单的程序中使用该函数，以演示该函数是如何工作的。
第三题，while (input[0] != 'q')，如果我输入的单词第一个字母为q的话不是不可以转化为小写嘛。
emmm……你是对的，我没考虑到这种情况