实验5

task1-1

#include <stdio.h>
#define N 5

void output(int x[], int n);

int main()
{
    int x[N] = {9, 55, 30, 27, 22};
    int i;
    int k;
    int t;
    
    printf("original array: \n");
    output(x, N);
    
    k = 0;
    for(i=1;i<N;++i)
       if(x[i]>x[k])
          k = i;
          
    if(k !=N-1)
    {
        t = x[N-1];
        x[N-1] = x[k];
        x[k] = t;
     } 
     
     printf("after swapped: \n");
     output(x, N);
     
     return 0;
 } 
 
 void output(int x[], int n)
 {
     int i;
     
     for(i=0;i<n;++i)
        printf("%d", x[i]);
        
        printf("\n");
 }

task1-2

#include <stdio.h>
#define N 5

void output(int x[], int n);

int main()
{
    int x[N] = {9, 55, 30, 27, 22};
    int i;
    int t;
    
    printf("original array: \n");
    output(x, N);
    
    for(i=0;i<N-1;++i)
       if(x[i]>x[i+1])
        {
            t = x[i];
            x[i] = x[i+1];
            x[i+1] = t;
        }
          
    
     printf("after swapped: \n");
     output(x, N);
     
     return 0;
 } 
 
 void output(int x[], int n)
 {
     int i;
     
     for(i=0;i<n;++i)
        printf("%d", x[i]);
        
        printf("\n");
 }

第一个交换了一次，第二个交换了三次

第一个是把最大元素向后放，而第二个是比较两者间的较小值往前放

task2

#include <stdio.h>

#define N 5

int binarySearch(int x[], int n, int item);

int main()
{
    int a[N] = {2, 7, 19, 45, 66};
    int i, index, key;
    
    printf("数组a中的数据: \n");
    for (i=0;i<N;++i)
        printf("%d", a[i]);
    printf("\n");
    
    printf("输入待查找的数据项： "); 
    scanf("%d", &key);
    index = binarySearch(a, 5, key);
    
    if (index >= 0)
       printf("%d 在数组中,下标为%d\n", key, index);
    else
       printf("%d 不在数组中\n", key);
       
       return 0; 
}





int binarySearch(int x[], int n, int item)
{
    int low, high, mid;
    
    low = 0;
    high = n - 1;
    
    while(low <= high)
    {
        mid = (low + high)/2;
        
        if(x[mid] == item)
        return mid;
        else if(x[mid] > item)
        high = mid - 1;
        else
        low = mid + 1;
    }
    
    return -1;
 }

 task3

#include <stdio.h>

#include<string.h>

#define N 5
void selectSort(char str[][20], int n);

int main()
{
   char name[][20] = {"Bob", "Bill", "Joseph", "Taylor", "George"};
   int i;
   
   printf("输出初始名单:\n");
   for (i = 0; i < N; i++)
       printf("%s\n", name[i]);
       
   selectSort(name, N);
    
   printf("按字典序输出名单:\n");
   for (i = 0; i < N; i++)
       printf("%s\n", name[i]);
   return 0;
}
void selectSort(char str[][20], int n)
{

   char temp[20];
   int i,j;
   for(i=0;i<n-1;i++){
        for(j=i+1;j<n;j++){
            if(strcmp(str[j],str[i])<0)
            {
               strcpy(temp,str[j]);
               strcpy(str[j],str[i]);
               strcpy(str[i],temp);
            }
    }
    
}
}

 task4

#include <stdio.h>

int main()
{
   int n;
   int *pn;
   
   n = 42;
   pn = &n;
   
   printf("&n = %#x, n = %d\n", &n, n);
   printf("&pn = %#x, pn = %#x\n", &pn, pn);
   printf("*pn = %d\n", *pn);
   
   return 0;
}

 n的地址是0x62felc 存放的是42

pn的地址是0x62fe10 存放的是n的地址0x62felc

通过*pn间接访问的是n

task5

#include <stdio.h>

#define N 5

int main()
{
    int a[N]= {1, 9, 2, 0, 7};
    int i;
    int *p;
    
    for(i=0; i<N; ++i)
       printf("&a[%d] = %#x, a[%d] = %d\n", i, &a[i], i, a[i]);
       
    printf("\n");
    
    for(i=0; i<N; ++i)
       printf("a+%d = %#x, *(a+%d) = %d\n", i, a+i, i, *(a+i));
       
    printf("\n");
    
    p = a;
    for(i=0; i<N; ++i)
       printf("p+%d = %#x, *(p+%d) = %d\n", i, p+i, i, *(p+i));
       
    return 0;
}

 都可以

都可以