程序设计与算法 第八、九周测验

1:指针练习：输出Hello

#include <iostream>
using namespace std;
int main() {
char s[] = "Hello";
char * p;
for(
// 在此处补充你的代码
p=s;*p!='\0';p++
)
cout << * p ;
return 0;
}

2:指针练习:输出Tesla

#include <iostream>
using namespace std;
void Print(const char * p1, const char * p2)
{
for(;p1<p2;p1++
// 在此处补充你的代码
)
cout << * p1;
}
int main()
{
const char * s = "Tesla123";
Print(s,s+5);
cout << endl;
Print(s,s+3);
cout << endl;

return 0;
}

3:指针练习：ForEach

#include <iostream>
using namespace std;

void ForEach(void * a, int width, int num,
// 在此处补充你的代码
void(*f)(void *)
)

{
for(int i = 0;i < num; ++i)
f((char*)a+width*i);
}

void PrintSquare(void * p)
{
int * q = (int*)p;
int n = *q;
cout << n * n << ",";
}
void PrintChar(void * p) {
char * q = (char*)p;
cout << *q << ",";
}
int main()
{
int a[5] = {1,2,3,4,5};
char s[] = "hello!";
ForEach(a,sizeof(int),5,PrintSquare);
cout << endl;
ForEach(s,sizeof(char),6,PrintChar);
return 0;
}

4:指针练习：Memcpy之一

#include <iostream>
using namespace std;
void Memcpy(char * src,char * dest,int n)
{
// 在此处补充你的代码
while(n--)
*dest++ = *src++;
}
int Strlen(char * s)
{
int i;
for( i = 0; s[i]; ++i);
return i;
}
int main()
{
int a;
char s1[30];
char s2[30];
int t;
cin >> t;
for(int i = 0;i < t; ++i) {
cin >> a;
int b = 99999999;
Memcpy((char*)&a,(char *) &b,sizeof(int));
cout << b << endl;
}
for(int i = 0;i < t; ++i) {
cin >> s1;
Memcpy(s1,s2,Strlen(s1)+1);
cout << s2 << endl;
}
return 0;
}

5:指针练习：double

#include <iostream>
using namespace std;

void Double(int * p, int n)
{
for(int i = 0;i < n; ++i)
p[i] *= 2;
}

int main()
{
int a[3][4] = { { 1,2,3,4},{5,6,7,8},
{ 9,10,11,12 } };

Double(
// 在此处补充你的代码
a[0]+4,6
);
for(int i = 0;i < 3; ++i) {
for(int j = 0; j < 4; ++j)
cout << a[i][j] << ",";
cout << endl;
}

return 0;
}

6:指针练习：Memcpy之二

#include <iostream>
using namespace std;
void Memcpy( void * src, void * dest, int size)
{
// 在此处补充你的代码
if (src < dest) {
while(size--)
((char *)dest)[size] = ((char *)src)[size];
} else if (src > dest) {
for(int n=0;n<size;n++)
((char *)dest)
= ((char *)src)
;
} else {
return;
}
}

void Print(int * p,int size)
{
for(int i = 0;i < size; ++i)
cout << p[i] << ",";
cout << endl;
}

int main()
{
int a[10];
int n;
cin >> n;
for(int i = 0;i < n; ++i)
cin >> a[i];
int b[10] = {0};
Memcpy(a,b,sizeof(a));
Print(b,n);

int c[10] = {1,2,3,4,5,6,7,8,9,10};
Memcpy(c,c+5,5*sizeof(int)); //将c的前一半拷贝到后一半
Print(c,10);

char s[10] = "123456789";
Memcpy(s+2,s+4,5); //将s[2]开始的5个字符拷贝到s[4]开始的地方
cout << s << endl;

char s1[10] = "123456789";
Memcpy(s1+5,s1+1,4); //将s1[5]开始的4个字符拷贝到s1[1]开始的地方
cout << s1 << endl;

return 0;
}

7:指针练习：MyMax

#include <iostream>
using namespace std;
// 在此处补充你的代码
void *MyMax(void *src, int size, int n, int(*f)(void*,void*))
{
char *p = (char *)src;
char *max = p;
for(;n--;p += size)
if (f(p, max) > 0)
max = p;
return max;
}
int Compare1(void * n1,void * n2)
{
int * p1 = (int * )n1;
int * p2 = (int * )n2;
return ((*p1)%10) - ((*p2)%10);
}
int Compare2(void * n1,void * n2)
{
int * p1 = (int * )n1;
int * p2 = (int * )n2;
return *p1 - *p2;
}
#define eps 1e-6
int Compare3(void * n1,void * n2)
{
float * p1 = (float * )n1;
float * p2 = (float * )n2;
if( * p1 - * p2 > eps)
return 1;
else if(* p2 - * p1 > eps)
return -1;
else
return 0;
}

int main()
{
int t;
int a[10];
float d[10];
cin >> t;
while(t--) {
int n;
cin >> n;
for(int i = 0;i < n; ++i)
cin >> a[i];
for(int i = 0;i < n; ++i)
cin >> d[i];
int * p = (int *) MyMax(a,sizeof(int),n,Compare1);
cout << * p << endl;
p = (int *) MyMax(a,sizeof(int),n,Compare2);
cout << * p << endl;
float * pd = (float * )MyMax(d,sizeof(float),n,Compare3);
cout << * pd << endl;
}
return 0;
}

8:指针练习：指向指针的指针

#include <iostream>
using namespace std;
int main()
{
int x,y,z;
x = 10;
y = 20;
z = 30;

int * a[3]  = { &x, &y,&z};
for(
// 在此处补充你的代码
int **p = a;
p < a + 3; ++p)
cout<< * (*p) << endl;
return 0;

}

9:指针练习：SwapMemory

#include <iostream>
using namespace std;
void SwapMemory(void * m1,void * m2, int size)
{
// 在此处补充你的代码
for(int n=0;n<size;n++)
{
char c = ((char *)m1)
;
((char *)m1)
= ((char *)m2)
;
((char *)m2)
= c;
}
}

void PrintIntArray(int * a,int n)
{
for(int i = 0;i < n; ++i)
cout << a[i] << ",";
cout << endl;
}

int main()
{
int a[5] = {1,2,3,4,5};
int b[5] = {10,20,30,40,50};
SwapMemory(a,b,5 * sizeof(int));
PrintIntArray(a,5);
PrintIntArray(b,5);
char s1[] = "12345";
char s2[] = "abcde";
SwapMemory(s1,s2,5);
cout << s1 << endl;
cout << s2 << endl;
return 0;
}