后序线索二叉树

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<algorithm>
 5
 6 using namespace std;
 7
 8 struct TREE{
 9     int    val;
10     TREE *ch[2];
11     TREE *thread;//该节点的线索的下一个节点
12     TREE(){}
13     TREE(int val){
14         this->val = val;
15         ch[0] = ch[1] = NULL;
16         thread = NULL;
17     }
18 };
19
20 void buildT(TREE * &T){
21     int x;
22     scanf("%d", &x);
23     if(x == -1) return ;
24
25     T = new TREE(x);
26     buildT(T->ch[0]);
27     buildT(T->ch[1]);
28 }
29
30
31 void postThread(TREE *T, TREE *pre){//感觉后序线索二叉树的思路和中序及前序的思路完全不一样啊
32     if(!T) return;
33     postThread(T->ch[0], T);
34     postThread(T->ch[1], T);
35     if(pre){
36         if(pre->ch[0] == T && pre->ch[1])//T是左子树
37             T->thread = pre->ch[1]; //T的下一个节点就是它的兄弟节点
38         else //T是右子树
39             T->thread = pre;//T的下一个节点就是它 的父亲节点
40     }
41 }
42
43 void printT_pre(TREE *T){//前序打印
44     if(!T) return ;
45     printf("%d ", T->val);
46     printT_pre(T->ch[0]);
47     printT_pre(T->ch[1]);
48 }
49
50 void printT_Thread(TREE *T){//后序线索打印
51     TREE *root = T;
52     bool flag = true;//表明T所在的字数没有访问过
53     while(1){
54         while(flag && T->ch[0]) T = T->ch[0];
55         printf("%d ", T->val);
56         if(T->thread->ch[0] == T || T->thread->ch[1] == T)
57             flag = false;//如果 T没有兄弟节点了，就一直沿着它的父节点向上走
58         else flag = true;
59         T = T->thread;
60         if(T == root){//再次回到最顶端父节点时， 结束！
61            printf("%d ", T->val);
62            break;
63         }
64     }
65 }
66
67 int main(){
68     TREE *T = NULL;
69     buildT(T);
70     printT_pre(T);
71     printf("\n");
72     postThread(T, NULL);
73     printT_Thread(T);
74     printf("\n");
75     return 0;
76 }