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 }