实验五

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;      // 用于记录最大元素的下标
    int t;      // 用作交换两个数组元素的中间变量

    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");
}

 

 

#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;      // 用作交换两个数组元素的中间变量

    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");
}

task1-1.c实现方式中，相较于原始数组，发生数组元素值交换  1次

task1-2.c实现方式中，相较于原始数组，发生数组元素值交换  3次

 

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,N,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;
}

 

 

 

task3-1

 

 

#include <stdio.h>
#define N 5

void selectSort(int a[], int n);
void input(int a[], int n);
void output(int a[], int n);

int main()
{
    int a[N];
    
    printf("输入%d个整数\n", N);
    input(a, N);
    
    printf("排序前的数据:\n");
    output(a, N);
    
    selectSort(a, N); 
    
    printf("排序后的数据:\n");
    output(a, N);
    
    return 0;
}

void input(int a[], int n)
{
    int i;
    
    for (i = 0; i < n; i++)
        scanf("%d", &a[i]);
}

void output(int a[], int n)
{
    int i;
    
    for (i = 0; i < n; i++)
        printf("%d ", a[i]);
    printf("\n");
}

void selectSort(int a[], int n)
{
    int i, j, k, temp;
    for (i = 0; i < n - 1; i++)
    {
        k = i;
        
        for (j = i + 1; j < n; j++)
            if (a[j] < a[k])
                k = j; 
                
        if (k != i)
        {     
            temp = a[i];
            a[i] = a[k];
            a[k] = temp;
        }
        
    }
    
}

task3-2

 

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

 

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;
    
}

 

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; 
               
}