[LeetCode系列] 从中序遍历和后序遍历序列构造二叉树(迭代解法)

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
13         if(inorder.size() == 0)return NULL;
14         TreeNode *p;
15         TreeNode *root;
16         stack<TreeNode *> stn;
17         
18         root = new TreeNode(postorder.back()); 
19         stn.push(root); 
20         postorder.pop_back(); 
21         
22         while(true)
23         {
24             if(inorder.back() == stn.top()->val) 
25             {
26                 p = stn.top();
27                 stn.pop(); 
28                 inorder.pop_back(); 
29                 if(inorder.size() == 0) break;
30                 if(stn.size() && inorder.back() == stn.top()->val)
31                     continue;
32                 p->left = new TreeNode(postorder.back()); 
33                 postorder.pop_back();
34                 stn.push(p->left);
35             }
36             else 
37             {
38                 p = new TreeNode(postorder.back());
39                 postorder.pop_back();
40                 stn.top()->right = p; 
41                 stn.push(p); 
42             }
43         }
44         return root;
45     }
46 };