1-9 编写一个将输入复制到输出的程序，并将其中连续的多个空格用一个空格代替

#include<stdio.h>

int main()
{
    int c_in, last_in;
    
    c_in = 0;
    last_in = 'a';

    while( (c_in=getchar()) != EOF )
    {
       if( c_in != ' '){
            putchar(c_in);
            last_in = c_in;
       }
       if( c_in == ' ' ){
            if( last_in != ' ' ){
                putchar(c_in);
                last_in = c_in;
            }
       }
    }

    return 0;
}