第八章 编程练习答案
1.
一开始没看懂题目意思，百度参考了一下别人的结果。
#include <iostream>
using namespace std;
int count = 0;
void Printf(const char * str, int n = 0);//默认参数
int main()
{
const char* str = "hello!";
Printf(str);
Printf(str, 1);
Printf(str, 0);
Printf(str, -1);
return 0;
}
void Printf(const char * str, int n)
{
count++;
if(n == 0)
cout << str << endl;
else{
for(int i = 0; i < count ; i++)
cout << str << endl;
}
cout << "-----------------" << endl;
}
2.
没有做到多用const，下次再说吧。
#include <iostream>
#include <cstring>
using namespace std;
const char size = 20;
struct CandyBar{
char brand[size];
double weight;
int calories;
};
void fill(CandyBar & fc, char * fb = "Millennium Munch", double weight = 2.85, int calories = 350);
//注意结构的引用
void show(CandyBar const & fc);
int main()
{
CandyBar a, b;
cout << "The brand #1: \n";
fill(a);//这里用了默认参数
show(a);
cout << endl;
char brand[size];
double weight;
int calories;
cout << "Please enter the brand: ";
cin.getline(brand, size);
cout << "Please enter the weight: ";
cin >> weight;
cout << "Please enter the calories: ";
cin >> calories;
cout << endl;
cout << "The brand #2: \n";
fill(b, brand, weight, calories);
show(b);
return 0;
}
void fill(CandyBar & fc, char * fb, double weight, int calories)
{
strcpy(fc.brand, fb);
//字符串的复制用了cstring中的strcpy，不能直接用赋值=，不能将指针赋值给常量
fc.weight = weight;
fc.calories = calories;
}
void show(CandyBar const & fc)
{
cout << "Brand: " << fc.brand << endl;
cout << "Weight: " << fc.weight << endl;
cout << "Calories: " << fc.calories << endl;
}3.
#include <iostream>
#include<cstring>
#include<cctype>
using namespace std;
void change(string &f);
int main()
{
string input;
cout << "Enter a string (q to quit): ";
getline(cin, input);
while ( input[0] != 'q' || input.size() > 1)//string.size()获取string的长度
//控制输入条件，只有输入q时退出，首字母为q后面有其他内容不退出
{
change(input);
cout << input << endl;
cout << "Enter a string (q to quit): ";
getline(cin, input);
}
cout << "bye" <<endl;
return 0;
}
void change(string &f)
{
for(int i = 0; i < f.size(); i++)
{
f[i] = toupper(f[i]);//转换大写
}
}
4.
#include <iostream>
#include <cstring>
using namespace std;
struct stringy{
char * str;
int ct;
};
void set(stringy & s, char * ch);
//引用参数，注意这里结构成员是一个指向char的指针
void show(stringy & s, int n = 1);
void show(char * fc, int n = 1);
//默认参数
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!");
return 0;
}
void set(stringy & s, char * ch)
{
s.ct = strlen(ch);//获取字符长度
s.str = ch;
}
void show(stringy & s, int n)
{
for(int i = 0; i < n; i++)
cout << s.str << endl;
cout << endl;
}
void show(char * fc, int n)
{
int count = 0, j = 0;
count = strlen(fc);//获取字符长度
while(j < n)//控制显示次数
{
for(int i = 0; i < count; i++)
cout << fc[i];//char类型逐个显示
cout << endl;
j++;
}
cout << endl;
}5.
#include <iostream>
using namespace std;
template <typename T>
T max5(T str[5]);//模板函数
int main()
{
int s1[5];
cout << "Please enter five int numbers: " << endl;
for (int i = 0; i < 5; i++)
cin >> s1[i];
cout << "The max is: " << max5(s1) << endl;
double s2[5];
cout << "Please enter five double numbers: " << endl;
for (int i = 0; i < 5; i++)
cin >> s2[i];
cout << "The max is: " << max5(s2) << endl;
return 0;
}
template <typename T>
T max5(T str[5])
{
T temp = str[0];
for(int i = 0; i < 5; i++ )
{
if(str[i] > temp)
temp = str[i];
}
return temp;
}
6.
#include <iostream>
#include <cstring>
using namespace std;
template <typename T>
T maxn(T str[], int n);//模板函数
template <> char *maxn(char *p[], int n);
//返回最长的字符串的地址
int main()
{
int n;
cout << "Please enter lentrh of array: " << endl;
cin >> n;
int s1[n];
cout << "Please enter numbers: " << endl;
for (int i = 0; i < n; i++)
cin >> s1[i];
cout << "The max is: " << maxn(s1,n) << endl;
cout << "Please enter lentrh of array: " << endl;
cin >> n;
double s2[n];
cout << "Please enter numbers: " << endl;
for (int i = 0; i < n; i++)
cin >> s2[i];
cout << "The max is: " << maxn(s2,n) << endl;
char *s3[5] = {"Monday", "Tuesday", "Wednesday", "Thursday", "Friday" };
cout << endl << "Monday , Tuesday , Wednesday , Thursday , Friday" << endl;
cout << "The address of max is: " << maxn(s3, 5) << endl;
return 0;
}
template <typename T>
T maxn(T str[], int n)
{
T temp = str[0];
for(int i = 0; i < n; i++ )
{
if(str[i] > temp)
temp = str[i];
}
return temp;
}
template <> char *maxn(char *p[], int n)//具体化模板
{
int max = 0;
char * temp = p[0];
for(int i = 0; i < n; i++)
{
if((int)strlen(p[i])> max)//注意比较地址长度
{
max = strlen(p[i]);
temp = p[i];
}
}
return temp;
}7.
#include <iostream>
using namespace std;
//修改函数返回类型和函数结构
//增加显示数组的和
template <typename T>
int ShowArray(T arr[], int n);
template <typename T>
double ShowArray(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 counts of things:\n";
int thingsum;
thingsum = ShowArray(things, 6);
cout << "The sum of things:" << thingsum << endl << endl;
cout << "Listing Mr.E's debts:\n";
double debtsum;
debtsum = ShowArray(pd, 3);
cout << "The sum of debts:" << debtsum << endl << endl;
return 0;
}
template <typename T>
int ShowArray(T arr[], int n)
{
int sum = 0;
cout << "template A\n";
for (int i =0; i < n; i++)
{
cout << arr[i] << ' ';
sum += arr[i];
}
cout << endl;
return sum;
}
template <typename T>
double ShowArray(T * arr[], int n)
{
double sum = 0.0;
cout << "template B\n";
for (int i =0; i < n; i++)
{
cout << *arr[i] << ' ';
sum += *arr[i];
}
cout << endl;
return sum;
}