串的堆分配存储结构

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
    char *a1=NULL;
    char *a2=NULL;
    a1=(char*)malloc(10*sizeof(char));
    strcpy(a1,"data.bian");   //将字符串"data.bian"复制给 a1
    a2=(char*)malloc(10*sizeof(char));
    strcpy(a2,"cheng.net");
    int lengthA1 = strlen(a1);//a1 串的长度
    int lengthA2 = strlen(a2);//a2 串的长度
    //尝试将合并的串存储在 a1 中，如果 a1 空间不够，则用 realloc 动态申请
    if(lengthA1 < lengthA1 + lengthA2)
    {
        a1=(char*)realloc(a1,(lengthA1+lengthA2+1)*sizeof(char));
    }
    //合并两个串到 a1 中
    for(int i=lengthA1;i<lengthA1+lengthA2;i++)
    {
        a1[i]=a2[i-lengthA1];
    }
    //串的末尾要添加 \0，避免出错
    a1[lengthA1+lengthA2]='\0';
    printf("%s\n",a1);
    //用完动态数组要立即释放
    free(a1);
    free(a2);
    return 0;


}

root@book-virtual-machine:/mnt/hgfs/lua/c++# g++ -std=c++11 salman_0119.cpp -o salman_0119
root@book-virtual-machine:/mnt/hgfs/lua/c++# ./salman_0119
data.biancheng.net
root@book-virtual-machine:/mnt/hgfs/lua/c++#