程序代码：

#include<stdio.h>
#define changdu 80
void main()
{
    char ch[changdu];
    int num,b,c,e;
    gets(ch);
    lddp: e=1;
    for (num=0;num<(changdu);num++)
    {    
        for (b=e;b<(changdu);b++)
        {
            if (ch[b]=='\0')
                goto loop;
            else
                if (ch[num]==ch[b])
                    {
                        for(c=b;c<(changdu-1);c++)
                            ch[c]=ch[c+1];
                        goto lddp;
                    }    
        }
        loop:e=e+1;    
    }
    puts(ch);
}