二级指针及多级指针的学习

用二级指针输出模型

#include<stdio.h>
#include<stdlib.h>
#include <string.h>
#include <ctype.h>


//求文件中两段话的长度
int getMen(char **myp1,int *mylen1,char **myp2,int *mylen2)
{
   char *tmp1 = NULL;
   char *tmp2 = NULL;

   tmp1 = (char *)malloc(100);
   if(tmp1 == NULL)
    return -1;

   strcpy(tmp1,"abcdefh");
   *mylen1 = strlen(tmp1);
   *myp1  = tmp1;

   tmp2 = (char *)malloc(100);
   if(tmp2 == NULL)
    return -2;

   strcpy(tmp2,"efghij");
   *mylen2 = strlen(tmp2);
   *myp2 = tmp2;
}

int getMen_free(char **myp1)
{
    char *tem = NULL;
    if(myp1 == NULL)
    {
        return -1;
    }
    tem = *myp1;

    free(tem);
    tem = NULL;
    return 0;
}

int main()
{
    char *p1 = NULL;
    int len1 = 0;

    char *p2 = NULL;
    int len2 = 0;
    int ret = 0;
    ret = getMen(&p1,&len1,&p2,&len2);
    printf("p1: %s\n",p1);
    printf("p2: %s\n",p2);
    getMen_free(&p1);
    getMen_free(&p2);

    return ret;
}

二级指针第一种输入模型

1.

 #include<stdio.h>
#include<stdlib.h>
#include <string.h>
#include <ctype.h>


//求文件中两段话的长度
int main()
{
    char *myArray[] = {"bbb","cccc","aaaa","2222"};

    int num = sizeof(myArray)/sizeof(myArray[0]);
    
    printf("返回前\n");
    for(int i=0;i<num;i++)
    {
        printf("%s\n",*(myArray+i));
    }

    char *temp = NULL;
    for(int i=0;i<num;i++)
    {
        for(int j=0;j<i;j++)
        {
            if(strcmp(myArray[i],myArray[j])>0)
            {
                temp = myArray[i];
                myArray[i] = myArray[j];
                myArray[j] = temp;
            }
        }
    }
    printf("返回后\n");
    for(int i=0;i<num;i++)
    {
        printf("%s\n",*(myArray+i));
    }
}

2.

 #include<stdio.h>
#include<stdlib.h>
#include <string.h>
#include <ctype.h>


void printfs(char **my,int len)
{
    printf("返回前\n");
    for(int i=0;i<len;i++)
    {
        printf("%s\n",*(my+i));
    }
}

void change(char **myArray,int num)
{
   char *temp = NULL;
    for(int i=0;i<num;i++)
    {
        for(int j=0;j<i;j++)
        {

            if(strcmp(myArray[i],myArray[j])>0)
            {
                printf("%d\n",strcmp(myArray[i],myArray[j]));
                printf("i:%s\n",myArray[i]);
                printf("j:%s\n",myArray[j]);
                temp = myArray[i];
                myArray[i] = myArray[j];
                myArray[j] = temp;
            }
        }
    }
}

//求文件中两段话的长度
int main()
{
    char *myArray[] = {"bbb","cccc","aaaa","2222"};

    int num = sizeof(myArray)/sizeof(myArray[0]);

    printfs(myArray,num);
    change(myArray,num);

   printfs(myArray,num);
}

二级指针模型，第二种输出模型

#include<stdlib.h>
#include<string.h>
#include<stdio.h>


int main()
{
    int i=0;
    char myBuf[30];
    char myArray[10][30]={"aaaaa","cccc","bbbb","111111111"};
    int num = 4;
    for(i=0;i<num;i++)
    {
        printf("%s\n",myArray[i]);
    }

    for(i=0;i<num;i++)
    {
        for(int j=i+1;j<num;j++)
        {
            if(strcmp(myArray[i],myArray[j])>0)
               {
                   strcpy(myBuf,myArray[i]);//交换的是内存块
                   strcpy(myArray[i],myArray[j]);
                   strcpy(myArray[j],myBuf);
               }
        }
    }
               for(i=0;i<num;i++)
    {
        printf("%s\n",myArray[i]);
    }
}