【leetcode】Construct Binary Tree from Inorder and Postorder Traversal

问题：

由中序和后序遍历构造二叉树。

分析：

Construct Binary Tree from Preorder and Inorder Traversal

//实现

TreeNode *addNode(vector<int> &inorder, int s1, int end1, vector<int> &postorder,  int s2, int end2)    {        if(s1 > end1 || s2 > end2)        return NULL;        //construct the root         TreeNode *root = new TreeNode(postorder[end2]);        //index_of_root: the index of root in inorder.        int i = s1;        for(; i <= end1; ++i)        {            if(inorder[i] == postorder[end2])               break;        }        if(i > end1)            return NULL;        int dist = i - s1;        //construct the left branch        root->left = addNode(inorder, s1, i - 1, postorder, s2, s2 + dist - 1);        //construct the right branch        root->right = addNode(inorder, i + 1 , end1, postorder, s2 + dist, end2 - 1);        return root;            }    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {        int inLen = inorder.size();        int posLen = postorder.size();        if(inLen == 0 || posLen == 0 || inLen != posLen)            return NULL;        TreeNode *root = addNode(inorder, 0, inLen - 1, postorder, 0, posLen - 1);        return root;    }