LeetCode Construct Binary Tree from Inorder and Postorder Traversal

题目：

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) {        TreeNode *root = createTree(inorder, 0, inorder.size()-1, postorder, 0, postorder.size()-1);        return root;    }    TreeNode *createTree(vector<int> &inorder, int inBeg, int inEnd, vector<int> &postorder, int postBeg, int postEnd) {        if(postBeg > postEnd)            return NULL;        int rootVal = postorder[postEnd];        int index;        for(int i = inBeg; i <= inEnd; i++) {            if(inorder[i] == rootVal) {                index = i;                break;            }        }        int len = index-inBeg;        TreeNode *root = new TreeNode(rootVal);        root->left = createTree(inorder, inBeg, index-1, postorder, postBeg, postBeg+len-1);        root->right = createTree(inorder, index+1, inEnd, postorder, postBeg+len, postEnd-1);        return root;    }};