LeetCode---(106)Construct Binary Tree from Inorder and Postorder Traversal

Given inorder and postorder traversal of a tree, construct the binary tree.

Note:

You may assume that duplicates do not exist in the tree.

/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* help(vector<int>& inorder, vector<int>& postorder,int fromi,int fromp,int length)
{
if(length==0)
return 0;
TreeNode* root=new TreeNode(postorder[fromp+length-1]);
int i;
for(i=fromi;inorder[i]!=postorder[fromp+length-1];i++)
;
root->left=help(inorder,postorder,fromi,fromp,i-fromi);
root->right=help(inorder,postorder,i+1,fromp+i-fromi,length-1-i+fromi);
return root;
}
TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
return help(inorder,postorder,0,0,inorder.size());
}
};