输出节点祖先（后序遍历顺序栈）

#include <stdio.h>
#include <stdlib.h>
#define MaxSize 50


typedef struct BiTNode{
    char data;
    struct BiTNode *lchild,*rchild;
}BiTNode,*BiTree;

typedef struct{
    BiTree ptr;
    int tag;      //=0表示左子女被访问，=1表示右子女被访问
}stack;

BiTree CreateBiTree( ){
    char ch;
    scanf("%c",&ch);
    if(ch=='#') return NULL;
    else{
        BiTree T = (BiTree)malloc(sizeof(BiTNode));
        T -> lchild  = T -> rchild = NULL;
        T->data = ch;
        T->lchild = CreateBiTree();
        T->rchild = CreateBiTree();
        return T;
    }
}

void Search(BiTree T ,  char ch){
    stack s[MaxSize];
    int top = -1 ;
    while( T!=NULL || top!=-1 ){
        while ( T!=NULL && T->data!=ch){
            s[++top].ptr = T;
            s[top].tag = 0;
            T = T->lchild;
        }
         if( T!=NULL && T->data==ch ){
            printf("该节点的所有祖先为：\n");
            for(int i = 0 ; i <= top ; i ++){
                printf( "%c",s[i].ptr->data );
            }
            exit(1);
        }
        while( top!=-1 && s[top].tag==1){
            top--;                         //左右孩子都访问过，指针减1
        }
        if(top!=-1){                      //如果左子树全部入栈，指针减1，访问右子树
            s[top].tag = 1;
            T = s[top].ptr->rchild;

        }

    }
}

int main()
{
    char ch ;
    printf("输入各节点：\n");
    BiTree T= CreateBiTree();
    printf("输入要查找的结点祖先：\n");
    scanf("%c",&ch);
    scanf("%c",&ch);
    Search(T,ch);
}