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) {}

 * };

 */

class Solution {

public:

    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) 

    {

        return build(inorder,0,inorder.size()-1,postorder,0,postorder.size()-1);

    }

    TreeNode *build(vector<int> &inorder,int inl,int inr, vector<int> &postorder,int pl,int pr)

    {

        if(inl>inr) return NULL;

        

        TreeNode *root=new TreeNode(postorder[pr]);

        int index=inl;

        while(inorder[index]!=postorder[pr]) index++;

        root->left=build(inorder,inl,index-1,postorder,pl,pl+index-inl-1);

        root->right=build(inorder,index+1,inr,postorder,pr-(inr-index),pr-1);

    }

};