程序设计与算法 | (16) Lecture(8) OJ作业

OJ地址

Lecture (8)包含以下九道编程题，可以在上面的OJ提交。

045:指针练习：输出Hello

#include <iostream>
using namespace std;
int main() {
    char s[] = "Hello";char * p;for(p=s;*p;p++)cout << * p ;return 0;
}

046:指针练习:输出Tesla

#include <iostream>
using namespace std;
void Print(const char * p1, const char * p2) 
{
      for(;p1<p2;p1++) 	cout << * p1;
}
int main()  
{
    const char * s = "Tesla123";Print(s,s+5);cout << endl;Print(s,s+3);cout << endl;return 0;
}

047:指针练习：ForEach

#include <iostream>
using namespace std;//函数指针
void ForEach(void * a, int width, int num,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;
}

048:指针练习：Memcpy之一

#include <iostream>
using namespace std;
void Memcpy(char * src,char * dest,int n) //逐字节拷贝
{
    for(int i=0;i<n;i++)*(dest+i) = *(src+i);
}
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;
}

049: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(a[1],6);for(int i = 0;i < 3; ++i) {
    for(int j = 0; j < 4; ++j)cout << a[i][j] << ",";cout << endl;}  return 0;
}

050:指针练习：Memcpy之二

#include <iostream>
using namespace std;
void Memcpy( void * src, void * dest, int size)
{
    char* src1 = (char*)src;char* dest1 = (char*)dest;//解决src和dest有重叠的问题if(src1>dest1)for(int i=0;i<size;i++)dest1[i] = src1[i];elsefor(int i=size-1;i>=0;i--)dest1[i] = src1[i];
}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;
}

051:指针练习：MyMax

#include <iostream>
using namespace std;void* MyMax(void* p,int element_size,int num,int (*f)(void*,void*))
{
    void * res = p;for(int i=1;i<num;i++)if(f(res,(char*)p+i*element_size)<0)res = (char*)p+i*element_size;return res;}
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;elsereturn 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;
}

052: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(int ** p=a;p < a + 3; ++p)cout<< * (*p) << endl;return 0;}

053:指针练习：SwapMemory

#include <iostream>
using namespace std;
void SwapMemory(void * m1,void * m2, int size)
{
    //逐字节交换char * p1 = (char*)m1;char * p2 = (char*)m2;for(int i=0;i<size;i++){
    char tmp = *(p1+i);*(p1+i) = *(p2+i);*(p2+i) = tmp;}
}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;
}