#include<stdio.h>

#include<stdlib.h>

#include <string.h>

char * mystrcpy(char * dest,char * src)

{

    if(dest==NULL||src==NULL)

    {

        return NULL;

    }

    char * bak=dest;

    while(*src!='\0')

    {

        *dest=*src;

        dest++;

        src++;

    }

    *dest='\0';//添加结束标识符

    return bak;

}

char * mystrncpy(char * dest,char * src,int count)

{

    if(dest==NULL||src==NULL)

    {

        return NULL;

    }

    char * bak=dest;

    while(*src!='\0'&&count>0)

    {

        *dest=*src;

        dest++;

        src++;

        count--;

    }

    *dest='\0';//添加结束标识符

    return bak;

}

int main()

{

    char dest[128]={'\0'};

    char dest2[128]={'\0'};

    char * src="helloworld";

    mystrcpy(dest,src);

    mystrncpy(dest2,src,3);

    printf("%s\n",dest);

    printf("%s\n",dest2);

    printf("done\n");

    return 0;

}