C language programming> 22nd week ⑤ In the following given program, the function of the function fun is to copy all the characters in the string p to the string a, and insert a space after every three characters copied.

Example: In the following given program, the function of the function fun is to copy all the characters in the string p to the string a, and insert a space after every three characters copied.

例如，在调用fun函数之前给字符串s输入asdf,调用函数之后，字符串a中的内容则为asd f。
注意：不要改动main函数，不能增行或删行，也不能更改程序的结构。

代码如下：

#include<stdio.h>
void fun(char*p,char*a)
{
    
    
	int i,j=0;
	while(*p)
	{
    
    
		i=0;
		while(i<3&&*p)
		{
    
    
			a[j]=*p;
			j++;
			p++;
			i++;
		}
		if(*p)
			a[j++]=' ';
	}
	a[j]='\0';
}
main()
{
    
    
	char s[80],a[80];
	printf("Enter a string: ");
	gets(s);
	printf("The original string: ");
	puts(s);
	fun(s,a);
	printf("\nThe string after insertspace: ");
	puts(a);
	printf("\n\n");
}

The output running window is as follows:

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