实验五

1_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, k, 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");
}

 1_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, k, 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");
}

1次

3次

一个交换元素的下标，一个交换元素

 

2

#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(item == x[mid])
            return mid;
        else if(item < x[mid])
            high = mid - 1;
        else
            low = mid + 1;
    }
    
    return -1;
}

 

 

3

#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; 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);
        }
    }
}

 

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;
}

0x62fe1c，42

0x62fe10，0x62fe1c

n

 

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

都可以

 

实验总结：

编写程序不能靠直觉，要有完整的推理