C语言字符串拷贝

C语言字符串拷贝利用指针操作，要清楚知道指针的指向

代码如下：

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

char* my_strcpy1(char* dest, const char* src)
{
        assert(dest != NULL && src != NULL);
        char* ret = dest;
        while((*dest++ = *src++) != '\0');
        return ret;
}
//较第一种效率高
char* my_strcpy2(char* dest, const char* src)
{
    assert(dest != NULL && src != NULL);
    char* s = (char*) src;
    //int delt = dest - src; //不兼容64位系统
　　 long delt = dest - src;
    while((s[delt] = *s++) != '\0');
    return dest;
}

int main(void)
{
        char str1[];
        char str2[];
        char str3[];  

        strcpy(str1,"sam");
        my_strcpy1(str2,"sam");
        my_strcpy2(str3,"sam");

        printf("str1 = %s\n", str1);
        printf("str1 = %s\n", str2);
        printf("str1 = %s\n", str3);

    return ;
}