实验一

 

task1_1.c

#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.c

#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");
}

 

 Q1:交换一次

task1-1，是直接找到最大数的下标

Q2：交换三次

task1-2，两两比较，择出较大数

实验二

 

#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;
}

 

 

 

 

 

 

 实验三

 

 

 

task 3-1.c

#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;
        }
    }
}

 

task 3-2.c

#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;
    char a[100];
    
    for(i=0; i<n-1; i++){                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
        for(j=i+1; j<n; j++){   
            if(strcmp(str[i], str[j])>0){
                strcpy(a, str[i]);
                strcpy(str[i], str[j]);
                strcpy(str[j], a);
            }
        }
    }
}

 

 实验四

#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;
}

 

 

 Q1：n的地址0x62fe1c，存放整数42

Q2：pn的地址0x62fe10，存放n的地址0x62fe1c

Q3：间接访问n的值

实验五

 

 

#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;
}

 

 

 Q1:可以    Q2：可以

实验总结

1.对二维数组的定义、初始化、元素引用的理解进一步加深

2.学习常见问题算法：选择排序，了解到与冒泡的区别；二分查找

3.对指针的概念进一步理解，&的作用更加明确