实验5

实验1.1

#include<stdio.h>
#define N 5
void output(int x[],int n)
{
    int i;
    for (i = 0; i < n; i++)
        printf("%d ", x[i]);
    printf("\n");
}
int main()
{
    int x[N] = { 9,55,30,27,22 };
    int i, k=0, t;
    printf("original array:\n");
    output(x, N);
    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;
}

 实验1.2

#include<stdio.h>
#define N 5
void output(int x[], int n)
{
    int i;
    for (i = 0; i < n; i++)
        printf("%d ", x[i]);
    printf("\n");
}
int main()
{
    int x[N] = { 9,55,30,27,22 };
    int i, 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;
}

 1.1交换了1次

 1.2交换了3次

第一种：先求最大数的下标，判断其是否为最大下标，若是，则最大值就是最后一个数，若不是，则两数值交换。

第二种：从前往后两两比较，使较大值始终位于后面。

实验2

#include<stdio.h>
#define N 5
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;
}
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", key, index);
    else
        printf("%d不在数组中\n", key);
    return 0;
}

 

实验3

 

#include<stdio.h>
#include<string.h>
#define N 5
void selectSort(char str[][20], int n)
{
    char a[20] = {'0'};
    int i, j;
        for (i = 0; i < n - 1; i++)   //冒泡排序
        {
            for (j = 0; j < n - 1 - i; j++)
                if (strcmp(str[j], str[j + 1]) > 0)
                {
                    strcpy(a, str[j]);
                    strcpy(str[j],str[j+1]);
                    strcpy(str[j + 1], a);
                }
        }
}
int main()
{
    char name[][20] = { "BOb","Bill","Joseph","Taylor","George" };
    int i;
    printf("输出初始者名单;\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;
}

 

 实验4

#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;

}

变量n的地址为0xf3fdec   变量n里存放的数为42

指针变量pn的地址为0xf3fde0  变量pn里存放的为变量n的地址

间接访问了变量n里存放的数 即42

实验5

#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;
}

都可以访问到数组a[i]

都可以获得元素a[i]的地址