1 #include<stdio.h>
 2 #include<stdlib.h>
 3 
 4 struct tNode
 5 {
 6    int data;
 7    struct tNode* left;
 8    struct tNode* right;
 9 };
10 
11 void MorrisTraversal(struct tNode *root)
12 {
13   struct tNode *current,*pre;
14 
15   if(root == NULL)
16      return; 
17 
18   current = root;
19   while(current != NULL)
20   {                 
21     if(current->left == NULL)
22     {
23       printf(" %d ", current->data);
24       current = current->right;      
25     }    
26     else
27     {
28       /* 找到current的前驱节点 */
29       pre = current->left;
30       while(pre->right != NULL && pre->right != current)
31         pre = pre->right;
32 
33       /* 将current节点作为其前驱节点的右孩子 */
34       if(pre->right == NULL)
35       {
36         pre->right = current;
37         current = current->left;
38       }
39 
40       /* 恢复树的原有结构，更改right 指针 */   
41       else 
42       {
43         pre->right = NULL;
44         printf(" %d ",current->data);
45         current = current->right;      
46       } /* End of if condition pre->right == NULL */
47     } /* End of if condition current->left == NULL*/
48   } /* End of while */
49 }
50 
51 struct tNode* newtNode(int data)
52 {
53   struct tNode* tNode = (struct tNode*)
54                        malloc(sizeof(struct tNode));
55   tNode->data = data;
56   tNode->left = NULL;
57   tNode->right = NULL;
58 
59   return(tNode);
60 }
61 
62 /* 测试*/
63 int main()
64 {
65 
66   /* 构建树结构如下：
67             1
68           /   69         2      3
70       /  71     4     5
72   */
73   struct tNode *root = newtNode(1);
74   root->left        = newtNode(2);
75   root->right       = newtNode(3);
76   root->left->left  = newtNode(4);
77   root->left->right = newtNode(5); 
78 
79   MorrisTraversal(root);
80    return 0;
81 }