一步一步复习数据结构和算法基础-后序线索二叉树

转自：http://blog.csdn.net/flying0033/article/details/6937477

后序线索二叉树的线索化有些麻烦：

1：若节点是二叉树的根，则后继为空；

2：若节点X是双亲的右孩子或者是双亲的左孩子且双亲没有右子树，则后继为双亲节点；

3：若双亲有左孩子而且双亲有右孩子，则后继为双亲右子树上面按后序遍历列出的第一个节点。

#include<stdio.h>#include<stdlib.h>#include<math.h>#define OK 1#define ERROR 0#define TRUE 1#define FALSE 0typedef enum{Link,Thread} PointTag;typedef char Element;typedef int Status;typedef struct Node{Element data;struct Node* left;  //指向左孩子struct Node* right; //指向右孩子PointTag Ltag;   //左右标志PointTag Rtag;}BitNode,*BitTree;Status visit(Element e);Status CreateTree(BitTree *T);void InThreading(BitTree T);void InOrderThreading(BitTree *H,BitTree T);void InOrderTraverse_Thr(BitTree L);BitTree pre;Status visit(Element e){printf("%c ",e);return OK;}Status CreateTree(BitTree *T) //前序创建二叉树{Element ch;scanf("%c",&ch);if(ch == '#')(*T) = NULL;else{(*T) = (BitTree)malloc(sizeof(BitNode));if(!(*T))exit(OVERFLOW);(*T)->data = ch;(*T)->Ltag = Link;(*T)->Rtag = Link;CreateTree(&(*T)->left);CreateTree(&(*T)->right);}return OK;}void InThreading(BitTree p) //后序线索二叉树{if(p){InThreading(p->left);InThreading(p->right);if(!p->left){p->left = pre;p->Ltag = Thread;}if(!pre->right){pre->right = p;pre->Rtag = Thread;}pre = p;}}void InOrderThreading(BitTree *H,BitTree T) //创建头节点,后序线索二叉树{(*H) = (BitTree)malloc(sizeof(BitNode));if(!(*H))exit(OVERFLOW);(*H)->right = (*H);(*H)->Rtag = Link;if(!T){(*H)->left = (*H);(*H)->Ltag = Link;}else{pre = (*H);(*H)->left = T;(*H)->Ltag = Link;InThreading(T);(*H)->right = pre;}}BitTree Parent(BitTree Thr,BitTree p)  //取得节点的父节点{BitTree temp = Thr;if(temp->left == p)return temp;else{temp = temp->left;while(temp->left != p && temp->right != p){if(temp->Rtag == Link)temp = temp->right;elsetemp = temp->left;  //有左孩子去左孩子,没有左孩子,去前驱;}}return temp;}void InOrderTraverse_Thr(BitTree Thr){BitTree temp = Thr->left;BitTree par = NULL;while(TRUE){while(temp->Ltag == Link)temp = temp->left;if(temp->Rtag == Link)temp = temp->right;elsebreak;}while(temp != Thr){visit(temp->data);par = Parent(Thr,temp);  //获得节点temp的父节点if(par == Thr) //若父节点是Thr则节点temp为根节点,无后继temp = Thr;else if(par->Rtag == Thread || temp == par->right) //无右兄弟的左节点或是右儿子temp = par;else//节点temp是左孩子,且有右兄弟{while(par->Rtag == Link){par = par->right;while(par->Ltag == Link){par = par->left;}}temp =par;}}}int main(){BitTree H,T;    printf("请输入前序二叉树的数据,例('ABDH##I##EJ###CF##G##')\n");    CreateTree(&T);    InOrderThreading(&H,T);    InOrderTraverse_Thr(H);    return 0;}