一步两步学算法之中序遍历线索二叉树

 1 typedef enum
 2 {
 3     SubTree,      //子树
 4     Thread        //线索
 5 }NodeFlag;
 6
 7 typedef struct ThreadTree
 8 {
 9     DATA data;
10     NodeFlag lflag;
11     NodeFlag rflag;
12     struct ThreadTree *left;
13     struct ThreadTree *right;
14 }ThreadBinTree;
15
16 ThreadBinTree *Previous=NULL;
17
18 void BinTreeThreading_LDR(ThreadBinTree *bt)    //二叉树按中序线索化
19 {
20     if(bt)
21     {
22         BinTreeThreading_LDR(bt->left);
23         bt->lflag=(bt->left)?SubTree:Thread;        //判断左子树有没有孩子
24         bt->rflag=(bt->right)?SubTree:Thread;
25         if(Previous)
26         {
27             if(Previous->rflag==Thread)                //判断前驱的右子树有没有孩子
28                 Previous->right=bt;                //把这个节点的地址赋给前驱的右子树
29             if(bt->lflag==Thread)                //判断这个节点的左子树有没有孩子
30                 bt->left=Previous;                //把前驱保存在这个节点的左子树中
31
32         }
33         Previous=bt;
34         BinTreeThreading_LDR(bt->right);
35     }
36 }
37 ThreadBinTree *BinTreeNext_LDR(ThreadBinTree *bt)  //求指定节点的后继
38 {
39     ThreadBinTree *nextnode;
40     if(!bt)
41         return NULL;
42     if(bt->rflag==Thread)
43         return bt->right;
44     else
45     {
46         nextnode=bt->right;
47         while(nextnode->lflag==SubTree)
48         {
49             nextnode=nextnode->left;
50         }
51         return nextnode;
52     }
53 }
54 ThreadBinTree *BinTreePrevious_LDR(ThreadBinTree *bt)
55 {
56     ThreadBinTree *prenode;
57     if(!bt)    return NULL;
58     if(bt->lflag==Thread)
59         return bt->left;
60     else
61     {
62         prenode=bt->left;
63         while(prenode->rflag==SubTree)
64             prenode=prenode->left;
65         return prenode;
66     }
67 }
68 void ThreadBinTree_LDR(ThreadBinTree *bt,void(*oper)(ThreadBinTree *p))  //遍历线索二叉树
69 {
70     if(bt)
71     {
72         while(bt->lflat==SubTree)
73             bt=bt->left;            //找最左下节点
74         do{
75             oper(bt);
76             bt=BinTreeNext_LDR(bt);
77         }while(bt);
78     }
79 }