c语言：编写一个将输入复制到输出的程序，并将其中的多个空格用一个空格代替

#include "stdio.h"

main()
{
int c;
int i;
int n = 0;

while ( (c = getchar()) != EOF)
{
if ( c != '' )
{
putchar(c);
}
else if ( n != '')
{
putchar(c);
}

n = c;
}
}

#include <stdio.h>

/* count lines in input */
int
main()
{
int c, pc; /* c = character, pc = previous character */

/* set pc to a value that wouldn't match any character, in case
this program is ever modified to get rid of multiples of other
characters */

pc = EOF;

while ((c = getchar()) != EOF) {
if (c == '')
if (pc != '')   /* or if (pc != c) */
putchar(c);

/* We haven't met 'else' yet, so we have to be a little clumsy */
if (c != '')
putchar(c);
pc = c;
}

return 0;
}