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;}};