首尾动态输出一个字符，最后将所有一串整的字符输出

输出welcome to bit!
#include <stdio.h>
#include <string.h>
#include <windows.h>
int main ()
{
int i=0;
int left=0;
char arr1[]="###############";
char arr2[]="welcome to bit!";
int size=strlen(arr1);
int right=size-1;
printf("%s\n",arr1);
for (i=0;i<(size+1)/2;i++)
{
arr1[left]=arr2[left];
arr1[right]=arr2[right];
left++;
right--;
printf("%s\n",arr1);
Sleep(1000)	;
}
return 0;
}