第九周C++作业（part 1）

/********理解指针的几种表现形式****************/
#include <iostream>
using namespace std;

int main()
{

int a=10;
int*p;
p=&a;
cout<<"a = "<<a<<endl;
cout<<"p = "<<p<<endl;
cout<<"&a = "<<&a<<endl;
cout<<"*p = "<<*p<<endl;
cout<<"&p = "<<&p<<endl;
cout<<endl;
*p=15;
cout<<"a = "<<a<<endl;
cout<<"p = "<<p<<endl;
cout<<"&a = "<<&a<<endl;
cout<<"*p = "<<*p<<endl;
cout<<"&p = "<<&p<<endl;

return 0;
}

/********输入两个整数，由大到小的顺序输出****************/
#include <iostream>
using namespace std;

int main()
{

int a,b,tp;
int *p=&a,*q=&b;
cout<<"please input a and b"<<endl;
cin>>a>>b;
if(a<b)
{
tp=*p;*p=*q;*q=tp;
}
cout<<"从大到小排序后的数为： "<<a<<"  "<<b<<endl;
cout<<"从大到小排序后的数为： "<<*p<<"  "<<*q<<endl;

return 0;
}

/********使用字符指针变量实现将字符串a赋值到字符串b中****************/
#include <iostream>
using namespace std;

int main()
{
char a[]="hello world",b[20],*p,*q;
p=a,q=b;
for(;*p!='\0';p++,q++)
*q=*p;
*q='\0';
cout<<"string1 is: ";
cout<<a<<endl;
cout<<"string2 is: ";
cout<<b<<endl;

return 0;

}

/********通过改变指针变量的值输出下面的字符串**********/
#include <iostream>
using namespace std;

int main()
{
char *p = "student";
for(;*p!='\0';p++)
cout<<p<<endl;

return 0;

}

/********用下标形式引用字符串中的字符**********/
#include <iostream>
using namespace std;

int main()
{
char *p ="student";
for(int i=0;p[i]!='\0';i++)
cout<<p[i];
cout<<endl;

return 0;

}

/********利用指针相减的运算，计算字符串的长度**********/
#include <iostream>
using namespace std;

int main()
{
char s[50];
char *p;
cout<<"please input a string: ";
cin.get(s,50);
p = s;
for(; *p!='\0';)
p++;
cout<<"the length is ："<<p-s<<endl;  //p指向最后一个地址，s指向第一个地址

return 0;

}

/********多级指针举例**********/
#include <iostream>
using namespace std;

int main()
{
int i =5,*p,**pp;
p=&i;
pp=&p;
cout<<&i<<'\t'<<i<<endl;
cout<<&p<<'\t'<<p<<'\t'<<*p<<endl;
cout<<&pp<<'\t'<<pp<<'\t'<<*pp<<'\t'<<**pp<<endl;
return 0;

}

/********指针数组举例**********/
#include <iostream>
using namespace std;

int main()
{
int a[5]={1,2,3,4,5};
int *p[5]={&a[0],&a[1],&a[2],&a[3],&a[4]};
for(int i = 0;i<5;i++)
cout<<*p[i]<<'\t';
cout<<endl;

return 0;

}

/********用字符串初始化字符指针数组**********/
#include <iostream>
using namespace std;

int main()
{
char *weekname[]={"sunday","monday","tuesday","wednesday","thursday","friday","saturday"};
int i;
while(1)
{
cout<<"please input week NO."<<endl;
cin>>i;
if(i<0||i>6)
break;
cout<<"week NO."<<i<<"-->"<<weekname[i]<<endl;
}

return 0;

}

/********将若干字符串按英文字典排序（由小到大）**********/
#include <iostream>
using namespace std;

int main()
{
char *p[]={"Rebacca","Heaven","Michael Chang","Linda Tsai"};
char * temp;
int i, j, n=4;
for(i=0;i<n-1;i++)
for(j=0;j<n-1-i;j++)
if(strcmp(p[j],p[j+1])>0)
{
temp=p[j],p[j]=p[j+1],p[j+1]=temp;
}
for(i=0;i<n;i++)
cout<<p[i]<<endl;

return 0;

}

/********用指针数组处理二维数组**********/
#include <iostream>
using namespace std;

int main()
{
int a[2][3],*p[2];
int i,j;
p[0]=a[0];
p[1]=a[1];
for(i=0;i<2;i++)
for(j=0;j<3;j++)
a[i][j]=j+i;
for(i=0;i<2;i++)
for(j=0;j<3;j++)
{
cout<<"a["<<i<<"]["<<j<<"]:";
cout<<*(p[i]+j)<<endl;
}
return 0;

}

/********利用二级指针处理二维数组**********/
#include <iostream>
using namespace std;

int main()
{
int a[2][3],*p[2],**pp;
int i,j;
p[0]=&a[0][0];
p[1]=&a[1][0];
pp=p;
for(i=0;i<2;i++)
for(j=0;j<3;j++)
pp[i][j]=j+i;
for(i=0;i<2;i++)
for(j=0;j<3;j++)
{
cout<<"a["<<i<<"]["<<j<<"]:";
cout<<*(*(pp+i)+j)<<endl;
}
return 0;

}

/********利用二级指针处理多个字符串**********/
#include <iostream>
using namespace std;

int main()
{
char *a[]={"Rebacca","Heaven","Michael Chang",NULL};
char **pp;
pp=a;
while(*pp!=NULL)          //为什么不是**pp!=NULL
cout<<*pp++<<endl;

return 0;

}

/********利用数组指针处理二维数组**********/
#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
int a[2][3] = {1,2,3,4,5,6};
int (*p)[3];
int i,j;
p=a;
for(i=0;i<2;i++)
{
for(j=0;j<3;j++)
cout<<setw(3)<<(*p)[j];
p++;
}
cout<<endl;

return 0;

}

/********指针作为函数参数的实例**********/
#include <iostream>
using namespace std;

void display(int *,int *);

int main()
{
int a=5,b=10;
int *pa = &a;
int *pb = &b;
display(pa,pb);

return 0;

}
void display(int *p1, int *p2)
{
cout<<"parameter 1 is "<<*p1<<endl;
cout<<"parameter 2 is "<<*p2<<endl;
}

/********通过指针变量调用函数**********/
#include <iostream>
using namespace std;

void display(int *,int *);

int main()
{
int func(int a,int b);
int(*pf)(int a,int b);	//定义一个函数指针变量pf
pf=func;				//将函数func的入口地址赋给了函数指针pf，从而使函数指针指向了该函数

cout<<"please input two integers: "<<endl;
int m,n;
cin>>m>>n;
int result=(*pf)(m,n);	//等价于reslut=func(m,n)
cout<<"the result is "<<result<<endl;
return 0;

}
int func(int a, int b)
{
return a+b;
}

/********设置一个函数process,在调用它的时候，每次实现不同的功能，
输入a和b两个数，第一次调用时找出a和b中大者，第二次调用找出a和b中
的小者，第三次调用时求a和b之和**********/
#include <iostream>
using namespace std;

int max(int x,int y)
{
int z;
if(x>y)z=x;
else z=y;
return z;
}
int min(int x,int y)
{
int z;
if(x<y)z=x;
else z=y;
return z;
}
int add(int x,int y)
{
int z;
z=x+y;
return z;

}
void process(int x,int y,int (*fun)(int,int))
{
int result;
result=(*fun)(x,y);
cout<<result<<endl;
}
int main()
{
int a,b;
cout<<"enter a and b: "<<endl;
cin>>a>>b;
cout<<"max = ";
process(a,b,max);
cout<<"min = ";
process(a,b,min);
cout<<"sum = ";
process(a,b,add);

return 0;

}