c++ primer Plus 第八章编程练习答案

8.1

#include<stdafx.h>
#include<iostream>
#include<string>
 using namespace std;
 void print(string p, int i = 0);//默认参数是在函数声明时指定的，函数定义时不能有默认参数
int main()
{
	string st = "c++";
	cout << "Test one parameter\n";
	print(st);
	cout << "Test two parameter\n";
	print(st, 3);
	return 0;

}

void print(string p,int i)//使用默认参数时的函数声明与不使用默认参数时相同
{
		
		cout << p<<endl;
		if (i>1)
		{
          print(p, --i);
		}
}

8.2

#include<stdafx.h>
#include<iostream>
#include<cstring>
#include<string>
 using namespace std;
 struct Candbar
 {
	 char brand[20];
	 double weight;
	 int qunantity;
 };
void set(Candbar &Can, char *s_p, double s_w, int s_q);
 void show(const Candbar & can);
int main()
{
	Candbar can;
	char brand[20] = "Millennium Munch";
	double weight = 2.85;
	int qunati = 350;
	set(can, brand, weight, qunati);
	show(can);
	return 0;

}

void set(Candbar &Can,char * s_p, double s_w, int s_q)
{
	 strcpy_s(Can.brand, s_p);
	/*Can.brand=*s_p是错误的，本意是想将s_p所指向的字符串
	赋给结构变量的brand成员，但是其为字符数组，数组名称表示其
	地址，即Can.brand为其地址，是一个右值可以将其赋给char指针，
	这里需要用字符串复制函数才能将其初始化为对应的字符串*/
	Can.weight = s_w;
	Can.qunantity = s_q;
}

void show(const Candbar & can)
{
	cout << "Brand is :" << can.brand << endl
		<< "weight is :" << can.weight << endl
		<< "qunantity is: " << can.qunantity << endl;
}

8.3

#include<stdafx.h>
#include<iostream>
#include<string>
#include<cctype>
 using namespace std;
 void s_toupper(string& str);
int main()
{
	string  str;
	cout << "enter a string(q to quit): ";
	getline(cin, str);
	while (str!="q")
	{
	  s_toupper(str);
	  cout << str << endl;
	  cout << "next string(q to quit): ";
      getline(cin, str);
	}
	cout << "Bye";
	return 0;
}

void s_toupper(string& str)
{
	for (int i = 0; str[i]; i++)
	{
		str[i] = toupper(str[i]);
	}
}

8.4

#include<stdafx.h>
#include<iostream>
#include<cstring>
struct stringy
{
	char *str;
	int ct;
};
using namespace std;
void set(stringy &stri1, char *testing);
void show(const stringy stri, int n = 1);
void show(const char * str, int n = 1);
int main()
{
	stringy beany = {NULL,0};
	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 &stri1, char *testing)
{
	stri1.ct= strlen(testing);
	stri1.str =new char(stri1.ct+1);
	strcpy(stri1.str, testing);
}
void show(const stringy stri, int n)
{
	for(int i=0;i<n;i++)
	{
		cout << stri.str[i]<<endl;
	}
}
void show(const char * str, int n)
{
	for (int i = 0; i <n; i++)
	{
		cout << str[i]<<endl;
	}
}

8.5

#include<stdafx.h>
#include<iostream>
#include<cstring>
using namespace std;
template<typename T>
T max5(T *arry);
int main()
{
	int int_a[5] = { 1,4,5,3,7 };
	double double_a[5] = { 1.2,2.4,3.5,2.1,4.5 };
	int int_max = max5(int_a);
	double double_max = max5(double_a);
	cout << int_max << endl
		<< double_max << endl;
	return 0;
}

template<typename T>
T max5(T *arry)
{
	T max = arry[0];
	for (int i = 1; i < 5; i++)
	{
		if (max<arry[i])
		{
			max = arry[i];
		}
	}
	return max;
}

8.6

#include<stdafx.h>
#include<iostream>
#include<cstring>
using namespace std;
template<typename T>
T maxn(T *arry,int n);
int main()
{
	int int_a[6] = { 1,4,5,3,7,6 };
	double double_a[4] = { 1.2,2.4,3.5,2.1 };
	int int_max = maxn(int_a,6);
	double double_max = maxn(double_a,4);
	cout << int_max << endl
		<< double_max << endl;
	return 0;
}

template<typename T>
T maxn(T *arry,int n)
{
	T max = arry[0];
	for (int i = 1; i < n; i++)
	{
		if (max<arry[i])
		{
			max = arry[i];
		}
	}
	return max;
}

8.7

#include<stdafx.h>
#include<iostream>
#include<cstring>
struct bebts
{
	char name[50];
	double amunt;
};
using namespace std;
template<typename T>
int SumArry(T * ar, int n);
template<typename T>
double SumArry(T *arr[], int n);
int main()
{
	bebts mr_E[3] = {
		{"Ima",2400.0},
	    {"Ura",1300.0},
	    {"Iby",1800.0}
	};
	int thing[6] = { 13,31,103,301,310,130 };
	double *p[3];
	for (int i = 0; i < 3; i++)
	{
		p[i] =&mr_E[i].amunt;
	}
	int t_sum = SumArry(thing, 6);
	double mr_sum = SumArry(p, 3);
	cout << t_sum << endl << mr_sum << endl;
	return 0;
}

template<typename T>
int SumArry(T * ar,int n)
{
	int sum = 0;
	for (int i = 0; i < n; i++)
	{
		sum = sum + ar[i];
	}
	return sum;
}
template<typename T> 
double SumArry(T *arr[], int n)
{
	double sum = 0.0;
	for (int i = 0; i < n; i++)
	{
		sum = sum + *arr[i];
	}
	return sum;
}