自己实现拷贝函数my_strcpy（依次逐步完善）

#include<stdio.h>
#include<assert.h>//为了引用assert

void my_strcpy1(char* arr1, char* arr2) {
  while (*arr2 != '\0') {
    *arr1 = *arr2;
    arr1++;
    arr2++;
  }
  *arr1 = *arr2;
}
void my_strcpy2(char* arr1, char* arr2) {
  while (*arr1++=*arr2++) {
    ;                                        //简洁
  }
}
void my_strcpy3(char* arr1, char* arr2) {
  assert(arr1 != NULL);
  assert(arr2 != NULL);                         //用来防止其中一个是空指针
  while (*arr1++ = *arr2++) {
    ;
  }
}
void my_strcpy4(char* arr1,const char* arr2) {
  assert(arr1 != NULL);
  assert(arr2 != NULL);
  while (*arr1++ = *arr2++) {                   //防止此处写反
    ;
  }
}
char* my_strcpy5(char* arr1, const char* arr2) {
  char* str = arr1;
  assert(arr1 != NULL);
  assert(arr2 != NULL);
  while (*arr1++ = *arr2++) {                
    ;
  }
  return str;                                   //链式访问
}
int main() {
  char arr1[] = "#######";
  char arr2[] = "abcd";
  printf("%s\n", arr1);
  //my_strcpy1(arr1, arr2);
  //my_strcpy2(arr1, arr2);
  //my_strcpy3(arr1, arr2);
  //my_strcpy4(arr1, arr2);
  printf("%s\n", my_strcpy5(arr1, arr2));
  //printf("%s\n", arr1);
  return 0;
}