编程练习答案第八章
8.1写输出字符串的函数，存在默认参数表示输出频率，莫感觉1.（原标题太扯了，的问题的细微变化的基础上，含义）
//8.1编写一个输出字符串的函数。有一个默认參数表示输出次数，默觉得1.（原题太扯啦，题意基础上小修改）
#include <iostream>
using namespace std; void show (const char* str, int time=1)
{
unsigned n=(time>0)? time:-time;
for (unsigned i = 0; i < n; ++i)
cout << str << endl;
cout << "-----------------" << endl;
} int main ()
{
const char* str = "hello word!";
show(str);
show(str,0);
show(str,1);
show(str,-1);
}
8.2CandyBar结构体有品牌，重量和热量3个成员，编写一个含有默认值的函数为成员赋值和一个显示内容函数
//8.2CandyBar结构体有品牌。重量和热量3个成员。编写一个含有默认值的函数为成员赋值和一个显示内容函数
//CandyBar& candbar, const char* strBrand = "Millennium Munch", double weight = 2.85, int calories = 350
#include <iostream>
#include <string>
using namespace std; struct CandyBar
{
string Brand;
double weight;
int calories;
}; void input (CandyBar& candbar, const char* Brand = "Millennium Munch", double weight = 2.85, int calories = 350)
{
candbar.Brand = Brand;
candbar.weight = weight;
candbar.calories = calories;
} void show (const CandyBar& candbar)
{
cout << candbar.Brand << '\t' << candbar.weight << '\t' << candbar.calories << endl;
} int main ()
{
CandyBar candbar1, candbar2;
input(candbar1);
show(candbar1);
input(candbar2, "world", 2,3 );
show(candbar2);
}
8.3编写一个函数。接受string引用。并把string内容变大写，之后利用循环測试
//8.3编写一个函数，接受string引用，并把string内容变大写，之后利用循环測试
#include <iostream>
#include <cctype>
using namespace std; string& upper (string& str)
{
for (char& e : str)
e = (char)toupper(e);
return (str);
} int main ()
{
while (true) {
cout << "Enter a string (q to quit): ";
string str;
getline(cin, str);
if (!cin || "q" == str || "Q" == str)
break;
cout << upper(str) << endl;
}
}
8.4按下面程序框架，完毕函数
//8.4按下面程序框架，完毕函数
#include <iostream>
#include <cstring>
using namespace std; struct stringy {
char * str;
int ct;
}; void set (stringy& stry, const char* szTxt)
{
stry.ct = (int)strlen(szTxt);
stry.str = new char [stry.ct + 1];
strcpy(stry.str, szTxt);
} void show (const char* szTxt, unsigned times = 1)
{
for (unsigned i = 0; i < times; ++i)
cout << szTxt << endl;
} void show (const stringy& stry, unsigned times = 1)
{
for (unsigned i = 0; i < times; ++i)
cout << stry.str << endl;
} void destroy (stringy& stry)
{
delete [] stry.str;
stry.str = NULL;
} int main()
{
stringy beany;
char testing[] = "Reality isn't what it used to be.";
set(beany, testing);
show(beany);
show(beany, 2);
destroy(beany);
testing[0] = 'D';
testing[1] = 'u';
show(testing);
show(testing, 3);
show("Done!");
}
8.5利用一个模板函数max5（）。返回给予的5个数的最大值(应用c++11的array)
//8.5利用一个模板函数max5（）。返回给予的5个数的最大值(应用c++11的array)
#include <iostream>
#include <array>
using namespace std; template<typename T>
const T& max5 (const array<T, 5>& arr)
{
unsigned max = 0;
for (unsigned i = 0; i < 5; ++i)
if (arr[i] > arr[max])
max = i;
return (arr[max]);
} int main ()
{
array<int, 5> iarray = {32, 20, 99, 256, 9};
for (const auto& e : iarray)
cout << e << ' ';
cout << " max: " << max5(iarray) << endl; array<double,5> darray = {1.2,2.3,4.5,32.3,4.3};
for (const auto& e : darray)
cout << e << ' ';
cout << "max: " << max5(darray) << endl;
}
8.6编写模板函数maxn(),參数为一个数组和元素数目。返回数组最大值，然后详细化一个字符串为元素的字符串，返回最长字符串
//8.6编写模板函数maxn(),參数为一个数组和元素数目，返回数组最大值，
//然后详细化一个字符串为元素的字符串，返回最长字符串
#include <iostream>
#include <cstring>
using namespace std; template <typename T>
const T& maxn (const T arr[], unsigned n)
{
unsigned max = 0;
for (unsigned i = 0; i < n; ++i)
if (arr[i] > arr[max])
max = i;
return (arr[max]);
} char* maxn ( char* arr[], unsigned n)
{
unsigned max = 0;
for (unsigned i = 0; i < n; ++i)
if (strlen(arr[i]) > strlen(arr[max]))
max = i;
return (arr[max]);
} int main ()
{
int iArray[] = {32, -1, 99, 0, 256, 9};
for (const auto& e : iArray)
cout << e << ' ';
cout << " ----max: " << maxn(iArray, sizeof(iArray)/sizeof(iArray[0])) << endl;
double dArray[] = {-3.2, 221.22, 9.9, 0, 1};
for (const auto& e : dArray)
cout << e << ' ';
cout << " ----max: " << maxn(dArray, sizeof(dArray)/sizeof(dArray[0])) << endl;
const char* szArray[] = {"aaaa","bbbbbb","cc","fffffffffff","kkkk"};
for (const auto& e : szArray)
cout << '\"' << e << '\"' << ' ';
cout << " ----max: " << '\"' << maxn(szArray, sizeof(szArray)/sizeof(szArray[0])) << '\"' << endl;
}
8.7对程序清单8.14,使用两个SumArray()模板返回数组元素总和。
程序返回thing以及debt的总和
//8.7对程序清单8.14,使用两个SumArray()模板返回数组元素总和。程序返回thing以及debt的总和
#include <iostream>
using namespace std; struct debts
{
char name[50];
double amount;
}; template <typename T>
double SumArray(T arr[], int n)
{
cout << "template A\n";
double sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return (sum);
} template <typename T>
double SumArray(T * arr[], int n)
{
cout << "template B\n";
double sum = 0;
for (int i = 0; i < n; i++)
sum += *arr[i];
return (sum);
} 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 << "the total number of Mr. E's things: " << SumArray(things, 6) << endl;
cout << "the sum of Mr. E's all debts: " << SumArray(pd, 3) << endl;
}
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