二级指针内存模型（三）

自定义内存，使用堆中分配内存来控制数据交换

交换指针指向的内容

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

int main()
{
    char **p2 = NULL;
    int i,j;
    int num = 5;
    p2 = (char **)malloc(sizeof(char *) * num);

    for(i = 0; i < num; i++)
    {
        p2[i] = (char *)malloc(sizeof(char) * 100);
        sprintf(p2[i],"%d%d%d",i+1,i+1,i+1);
    }        

    //print
    printf("before sort\n");
    for(i = 0; i < num; i++)
    {
        printf("%s \n",p2[i]);
    }

    char *tmp = NULL;
    //sort
    for(i = 0; i < num; i++)
    {
        for(j = i+1; j < num; j++)
        {
            if(strcmp(p2[i],p2[j]) < 0)
            {
                tmp = p2[i];
                p2[i] = p2[j];
                p2[j] = tmp;
            }
        }
    }

    printf("after sort\n");
    for(i = 0; i < num; i++)
    {
        printf("%s \n",p2[i]);
    }

    //free
    for(i = 0; i < num; i++)
    {
        if(p2[i] != NULL)
        {
            free(p2[i]);
            p2[i] = NULL;
        }
    }

    if(p2 != NULL)
    {
        free(p2);
    }
    return 0;
}

交换指针指向的内存块

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

int main()
{
    char **p2 = NULL;
    int i,j;
    int num = 5;
    char tmpbuf[100];
    p2 = (char **)malloc(sizeof(char *) * num);

    for(i = 0; i < num; i++)
    {
        p2[i] = (char *)malloc(sizeof(char) * 100);
        sprintf(p2[i],"%d%d%d",i+1,i+1,i+1);
    }        

    //print
    printf("before sort\n");
    for(i = 0; i < num; i++)
    {
        printf("%s \n",p2[i]);
    }

    char *tmp = NULL;
    //sort change the storage
    for(i = 0; i < num; i++)
    {
        for(j = i+1; j < num; j++)
        {
            if(strcmp(p2[i],p2[j]) < 0)
            {
                strcpy(tmpbuf,p2[i]);
                strcpy(p2[i],p2[j]);
                strcpy(p2[j],tmpbuf);
            }
        }
    }

    printf("after sort\n");
    for(i = 0; i < num; i++)
    {
        printf("%s \n",p2[i]);
    }

    //free
    for(i = 0; i < num; i++)
    {
        if(p2[i] != NULL)
        {
            free(p2[i]);
            p2[i] = NULL;
        }
    }

    if(p2 != NULL)
    {
        free(p2);
    }
    return 0;
}

函数封装接口

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

char **getMem(int num)
{
    char **p2 = NULL;
    int i;
    p2 = (char **)malloc(sizeof(char *) * num);
    if(p2 == NULL)
    {
        return NULL;
    }

    for(i = 0; i < num; i++)
    {
        p2[i] = (char *)malloc(sizeof(char) * 100);
        sprintf(p2[i],"%d%d%d",i+1,i+1,i+1);
    }        

    return p2;
}

void sortMyarray(char **myArray,int num)
{
     int i = 0,j = 0;
    char *tmp = NULL;
    //sort change the storage
    for(i = 0; i < num; i++)
    {
        for(j = i; j < num; j++)
        {
            if(strcmp(myArray[i],myArray[j]) < 0)
            {
                tmp = myArray[i];
                myArray[i] = myArray[j];
                myArray[j] = tmp;
            }
        }
    }
}

void printMyArray(char **myArray,int num)
{
    int i = 0;
    for(i = 0; i < num; i++)
    {
        printf("%s \n",*(myArray+i));
    }
}

void getMem_free(char **p2,int num)
{
    int i;
    for(i = 0; i < num; i++)
    {
        if(p2[i] != NULL)
        {
            free(p2[i]);
            p2[i] = NULL;
        }
    }

    if(p2 != NULL)
    {
        free(p2);
    }
}

int main()
{
    char **p2 = NULL;
    int i,j;
    int num = 5;
    char tmpbuf[100];

    p2 = getMem(num);
    //print
    printf("before sort\n");
    printMyArray(p2,num);

    sortMyarray(p2,num);

    printf("after sort\n");
    printMyArray(p2,num);

    //free
    getMem_free(p2,num);

    return 0;
}

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

int main()

{

char
**p2 = NULL;

int
i,j;

int
num = 5;

p2
= (char **)malloc(sizeof(char *) * num);

for(i
= 0; i < num; i++)

{

p2[i]
= (char *)malloc(sizeof(char) * 100);

sprintf(p2[i],"%d%d%d",i+1,i+1,i+1);

}

//print

printf("before
sort\n");

for(i
= 0; i < num; i++)

{

printf("%s
\n",p2[i]);

}

char
*tmp = NULL;

//sort

for(i
= 0; i < num; i++)

{

for(j
= i+1; j < num; j++)

{

if(strcmp(p2[i],p2[j])
< 0)

{

tmp
= p2[i];

p2[i] = p2[j];

p2[j]
= tmp;

}

}

}

printf("after
sort\n");

for(i
= 0; i < num; i++)

{

printf("%s
\n",p2[i]);

}

//free

for(i
= 0; i < num; i++)

{

if(p2[i]
!= NULL)

{

free(p2[i]);

p2[i]
= NULL;

}

}

if(p2
!= NULL)

{

free(p2);

}

return
0;

}

原文地址：https://www.cnblogs.com/wanghao-boke/p/11625376.html