Construct Binary Tree from Inorder and Postorder Traversal

递归，代码如下：

class Solution {public:    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {        return buildTree1(inorder, postorder, 0, 0, inorder.size());    }        TreeNode *buildTree1(vector<int> &inorder, vector<int> &postorder, int begin1, int begin2, int len) {        if(len == 0) return NULL;                TreeNode *left, *right, *rootNode;        int root = postorder[begin2+len-1];        int index = begin1;        for(; index<begin1+len; ++index) {            if(inorder[index] == root) {                rootNode = new TreeNode(root);                rootNode->left = buildTree1(inorder, postorder, begin1, begin2, index-begin1);                rootNode->right= buildTree1(inorder, postorder, index+1, begin2+(index-begin1), len-(index-begin1)-1);                return rootNode;            }        }    }};

9.02最新代码，注意细节：

class Solution {public:    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {        int len = inorder.size();        if(len == 0) return NULL;                return build(inorder, postorder, 0, 0, len);    }        TreeNode *build(vector<int> &inorder, vector<int> &postorder, int si, int sp, int len)    {        if(len<=0) return NULL;                TreeNode *root = new TreeNode(postorder[sp+len-1]);                for(int i=0; i<len; i++)        {            if(postorder[sp+len-1] == inorder[si+i])            {                root->left = build(inorder, postorder, si, sp, i);                root->right = build(inorder, postorder, si+i+1, sp+i, len-i-1);                return root;            }        }    }};