leetcode - 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 binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
struct TreeNode
{
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
class Solution {
public:
TreeNode *buildTree(std::vector<int> &inorder, std::vector<int> &postorder) {
return buildBinTree(inorder,0,inorder.size()-1,postorder,0,postorder.size()-1);
}
private:
TreeNode *buildBinTree(std::vector<int> &inorder,int inStart,int inEnd,std::vector<int> &postorder,int postStart,int postEnd)
{
if(inStart > inEnd || postStart > postEnd) return NULL;
TreeNode *root = new TreeNode(postorder[postEnd]);
int rootIndex = 0;
for (int i = inStart; i <= inEnd; i++)
{
if(inorder[i] == root->val)
{
rootIndex = i;
break;
}
}
int len = rootIndex - inStart;
root->left = buildBinTree(inorder,inStart,rootIndex-1,postorder,postStart,postStart+len-1);
root->right= buildBinTree(inorder,rootIndex+1,inEnd,postorder,postStart+len,postEnd-1);
return root;
}
};