c++.primer.plus第五版第八章编程练习答案

// 1
#include <iostream>
using namespace std;
void print(const char *str,int n = 1);
int main()
{
const char *str = "My English is very good + I can speak English Well！\n";
cout << "=====================================================================\n";
print(str);
cout << "=====================================================================\n";
print(str,10);
cout << "=====================================================================\n";
return 0;
}
void print(const char * str,int n)
{
if(n <= 0)
n = 1;
for(int i = 0;i < n;i++)
cout << str ;
}
// 2
#include <iostream>
#include <cstring>

using namespace std;

struct CandyBar
{
char name[50];
double weight;
int hot;
};
void fill_candybar(CandyBar &t,char * str,double w,int h);
void show_candybar(const CandyBar &t);
int main()
{
CandyBar t;
char str[50] = "Millennium Munch";
double w = 2.85;
int h = 350;

fill_candybar(t,str,w,h);
show_candybar(t);

return 0;
}
void fill_candybar(CandyBar &t,char * str,double w,int h)
{
strcpy(t.name,str);
t.weight = w;
t.hot = h;
}
void show_candybar(const CandyBar &t)
{
cout << "CandyBar.name = \t" << t.name << endl;
cout << "CandyBar.weight = \t" << t.weight << endl;
cout << "CandyBar.hot = \t\t" << t.hot << endl;
}
// 3                // 注意对string对象的判断
#include <iostream>
using namespace std;
void string_to_toupper(string & str);
void string_show(const string & str);
int main()
{
string str;
while(1)
{
cout << "Enter a string (q to quit): ";
getline(cin,str);
if(str == "q")
break;
string_to_toupper(str);
string_show(str);
}
return 0;
}
void string_to_toupper(string & str)
{
for(int i = 0;str[i] != '\0';i++)
str[i] = toupper(str[i]);
}
void string_show(const string & str)
{
cout << str << endl;
}
// 4
#include <iostream>
#include <cstring>          // for strlen(),strcpy()

using namespace std;
struct stringy{
char * str;             // points to a string
int ct;                 // length of string(not counting '\0')
};
// prototypes for set(),show(),and show() go here
void set(stringy &beany,char arr[]);
void show(const stringy sty,int n = 1);
void show(const char str[],int n = 1);
int main()
{
stringy beany;
char testing[] = "Reality isn't what it used to be. ";
set(beany,testing);     // first argument is a reference.
// allocates space to hold copy of testing,
// sets str member of beany to point to the
// new block,copies testing to new block,
// and set ct member of beany
show(beany);        // prints member string once
show(beany,2);      // prints member string twice
testing[0] = 'D';
testing[1] = 'u';
show(testing);      // prints testing string once
show(testing,3);    // prints testing string thrice
show("Done!" );

return 0;
}
void set(stringy &beany,char arr[])
{
int len = strlen(arr) + 1;
beany.str = new char[len];
strcpy(beany.str,arr);
beany.str[len] = '\0';
beany.ct = len - 1;
}
void show(const stringy sty,int n)
{
if(n <= 0)
n = 1;
for(int i = 0;i < n;i++)
{
cout << "stringy.str = \t" << sty.str << endl;
cout << "stringy.ct = \t" << sty.ct << endl;
}
}
void show(const char str[],int n)
{
if(n <= 0)
n = 1;
for(int i = 0;i < n;i++)
cout << str << endl;
}
// 5
#include <iostream>
using namespace std;
const  int len = 5;
template <class T>
T max5(const T ar[]);

int main()
{
int ari[] = {1,5,2,4,3};
double ard[] = {1.0,5.0,2.0,4.0,3.0};

cout << "ari-max = \t" << max5(ari) << endl;
cout << "ard-max = \t" << max5(ard) << endl;

return 0;
}
template <class T>
T max5(const T ar[])
{
T temp = ar[0];
for(int i = 1;i < len;i++)
if(temp < ar[i])
temp = ar[i];
return temp;
}
// 6            待验证
#include <iostream>
#include <cstring>
using namespace std;
template <class T>
T maxn(const T ar[],int n);
const char *  maxchlen(const char *str[],int n);
const char **  maxchlenaddr(const char *str[],int n);
int main()
{
int ari[] = {1,5,2,4,3};
double ard[] = {1.0,2.0,4.0,3.0};
const char *arst[5] = {
"aaaaaaaaaaaaaaaaaa",
"bbbbbbbbbbbbbbbbbbbbb",
"ccccccccccccccccccccccccccc",
"ddddddddddddddddddddddddddd",
"eeeeeeeeeeeeeeeeeeeeeeeeeee"
};
cout << "ari-max = \t" << maxn(ari,5) << endl;
cout << "ard-max = \t" << maxn(ard,4) << endl;
cout << "the theory address is\t" << &arst[2] << endl;
cout << "the real address is\t" << maxchlenaddr(arst,5) << endl;
cout << "the real address is\t" << maxchlen(arst,5) << endl;
return 0;
}
template <class T>
T maxn(const T ar[],int n)
{
T temp = ar[0];
for(int i = 1;i < n;i++)
if(temp < ar[i])
temp = ar[i];
return temp;
}
const char * maxchlen(const char *str[],int n)
{
unsigned temp = strlen(str[0]);
const char *add = str[0];
for(int i = 1;i < n;i++)
if(temp < strlen(str[i]))
{
temp = strlen(str[i]);
add = str[i];
}
return add;
}
const char **  maxchlenaddr(const char *str[],int n)
{
unsigned temp = strlen(str[0]);
const char **add = &str[0];
for(int i = 1;i < n;i++)
if(temp < strlen(str[i]))
{
temp = strlen(str[i]);
add = &str[i];
}
return add;
}
// 8.14 temptempover.cpp
// temptempover.cpp -- template overloading
#include <iostream>
template <typename T>
void ShowArray(T arr[],int n);              // template A

template <typename T>                       // template B
void ShowArray(T *arr[],int n);

struct debts
{
char name[50];
double amount;
};
int main(void)
{
using namespace std;
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];
// set pointers to the amount members of the structures in the arr mr_E
for(int i = 0;i < 3;i++)
pd[i] = &mr_E[i].amount;

cout << "Listing Mr.E's counts of things:\n";
// things is an array of int
ShowArray(things,6);        // uses template A
cout << "Listing Mr. E's debts: \n";
// pd is an array of pointers to double
ShowArray(pd,3);            // uses template B(more specialized)

return 0;
}
template <typename T>
void ShowArray(T arr[],int n)
{
using namespace std;
cout << "template A\n";
for(int i = 0;i < n;i++)
cout << arr[i] << ' ';
cout << endl;
}
template <typename T>
void ShowArray(T * arr[],int n)
{
using namespace std;
cout << "template B\n";
for(int i = 0;i < n;i++)
cout << *arr[i] << ' ';
cout << endl;
}
// 7
#include <iostream>
template <typename T>
long ShowArray(T arr[],int n);              // template A
template <typename T>                       // template B
double ShowArray(T *arr[],int n);
struct debts
{
char name[50];
double amount;
};
int main(void)
{
using namespace std;
int things[6] = {13,31,103,301,310,130};
long things_sum = 0;
struct debts mr_E[3] =
{
{"Ima Wolfe",2400.0},
{"Ura Foxe ",1300.0},
{"Iby Stout",1800.0}
};
double * pd[3];
double pd_sum = 0.0;
// set pointers to the amount members of the structures in the arr mr_E
for(int i = 0;i < 3;i++)
pd[i] = &mr_E[i].amount;

// things is an array of int
things_sum = ShowArray(things,6);        // uses template A
cout << "thing_sum = " << things_sum << endl;

// pd is an array of pointers to double
pd_sum = ShowArray(pd,3);            // uses template B(more specialized)
cout << "pd_sum = " << pd_sum << endl;

return 0;
}
template <typename T>
long ShowArray(T arr[],int n)
{
long arr_sum = 0;
using namespace std;
cout << "template A\n";
for(int i = 0;i < n;i++)
arr_sum = arr_sum + arr[i];

return arr_sum;
}
template <typename T>
double ShowArray(T * arr[],int n)
{
using namespace std;
double arr_sum;
cout << "template B\n";
for(int i = 0;i < n;i++)
arr_sum = arr_sum + *arr[i];

return arr_sum;
}