练习.txt

钱能主编 C++程序设计教程（第一版） 该书习题的答案代码

9.1
-----original codes-----
#include <iostream.h>

const size=10;

void findmax(int* a,int n,int i,int* pk);

void main()
{
	int a[size];
	int n=0;
	cout<<"please input "<<size<<" datas:"<<endl;
	for(int i=0;i<size;i++)
		cin>>a[i];

	findmax(a,size,0,&n);

	cout<<"The maximum is "<<a[n]<<endl
		<<"It's index is "<<n<<endl;
}

void findmax(int* a,int n,int i,int* pk)
{
	if(i<n)
	{
		if(a[i]>a[*pk])
			*pk=i;
		findmax(a,n,i+1,pk);
	}
}

-----answer version-----

#include <iostream.h>

const size=10;

void findmax(int* a,int n,int i,int& pk);

void main()
{
	int a[size];
	int n=0;
	cout<<"please input "<<size<<" datas:"<<endl;
	for(int i=0;i<size;i++)
		cin>>a[i];

	findmax(a,size,0,n);

	cout<<"The maximum is "<<a[n]<<endl
		<<"It's index is "<<n<<endl;
}

void findmax(int* a,int n,int i,int& pk)
{
	for(;i<n;i++)
	{
		if(a[i]>a[pk])
			pk=i;
	}
}

9.2
#include <iostream.h>
#include <stdlib.h>

int& put(int n);
int  get(int n);

int val[10];
int error=-1;

void main()
{
	put(0)=10;
	put(1)=20;
	put(9)=30;

	cout<<get(0)<<endl
		<<get(1)<<endl
		<<get(9)<<endl;

	put(12)=1;
}

int& put(int n)
{
	if(n>9||n<0)
	{
		error=1;
		cout<<"range error in put value!"<<endl;
		exit(1);
	}
	error=0;
	return val[n];
}

int get(int n)
{
	if(n>9||n<0)
	{
		error=1;
		cout<<"range error in get value!"<<endl;
		exit(1);
	}
	error=0;
	return val[n];
}

9.3
#include <iostream.h>
#include <iomanip.h>

void swap(char* (&a),char* (&b));

char* ap="hello";
char* bp="how are you?";

void main()
{
	cout<<"original:"<<endl
        <<"ap:	"<<ap<<endl
		<<"bp:	"<<bp<<endl;
	cout<<"&(*ap):"<<&(*ap)<<endl
		<<"&(*bp):"<<&(*bp)<<endl;

	swap(ap,bp);
	cout<<"changed:"<<endl
        <<"ap:	"<<ap<<endl
		<<"bp:	"<<bp<<endl;
	cout<<"&(*ap):"<<&(*ap)<<endl      //很奇怪，这里显示的仍然是字符串，不是地址，
		<<"&(*bp):"<<&(*bp)<<endl; //要显示地址的话，须在前面加（int）强制转换，
}

void swap(char* (&a),char* (&b))
{
	char* tmp;
	tmp=a;
	a=b;
	b=tmp;
}