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leetcode - Construct Binary Tree from Inorder and Postorder Traversal

2013-03-26 20:54  张汉生  阅读(272)  评论(0)  编辑  收藏  举报

题目描述：点击此处

此题如果直接采用原来的BuildTree递归会有Memory limit Exceed

 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>::iterator inBegin, vector<int>::iterator inEnd, 
13                         vector<int>::iterator postBegin, vector<int>::iterator postEnd){
14         int val = *(postEnd-1);
15         TreeNode * root = new TreeNode(val);
16         vector<int>::iterator ii, jj;
17         vector<int> leftIn, leftPost, rightIn, rightPost;
18         for (ii=inBegin, jj=postBegin; ii!=inEnd && *ii!=val; ii++, jj++);
19         if (ii!=inBegin)
20             root->left = buildTree(inBegin, ii, postBegin, jj);
21         if (ii+1 != inEnd)
22             root->right = buildTree(ii+1, inEnd, jj, postEnd-1);
23         return root;
24     }
25     TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
26         // Start typing your C/C++ solution below
27         // DO NOT write int main() function
28         if (inorder.empty())
29             return NULL;
30         return buildTree(inorder.begin(),inorder.end(),postorder.begin(), postorder.end());
31     }
32 };