#include<stdio.h>
#include<stdlib.h>

typedef enum{atom,list}nodeTag;

typedef struct node
{
    nodeTag tag;
    union
    {
        char data;
        node *slink;
    };
    node *link;
}pNode,*pist;

void cre(pist &p)
{
    char ch;
    scanf("%c",&ch);
    if(ch!=' ')
    {
        p=new pNode;
        if(ch=='(')
            cre(p->slink),p->tag=list;
        else
            p->tag=atom,p->data=ch;
    }
    else
        p=NULL;
    scanf("%c",&ch);
    if(p!=NULL)
    {
        if(ch==',')
            cre(p->link);
        else
            p->link=NULL;
    }
}

void show(pist p)
{
    if(p)
    {
        if(p->tag==list)
        {
            printf("(");
            if(p->slink==NULL)
                printf(" ");
            else
                show(p->slink);
        }
        else
            printf("%c",p->data);
        if(p->tag==list)
            printf(")");
        if(p->link!=NULL)
            printf(","),show(p->link);
    }
}

void main()
{
    pist p;
    cre(p);
    show(p);
}
看不明白这道程序,大家帮忙分析下,谢谢!!