LeetCode 106. 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.

class Solution {
public:

TreeNode* f(vector<int>& inorder,int l1,int r1, vector<int>& postorder,int l2,int r2) {
vector<int>::iterator re = find(inorder.begin()+l1,inorder.begin()+r1,*(postorder.begin()+r2));
int  numl = re - inorder.begin()-l1, numr = inorder.begin()+r1-re;
TreeNode* t = new TreeNode(*(re));
if(numl != 0) {
t->left = f(inorder,l1,re-inorder.begin()-1,postorder,l2,l2+numl-1);
} else {
t->left = NULL;
}
if(numr != 0) {
t->right = f(inorder,re-inorder.begin()+1,r1,postorder,r2-numr,r2-1);
} else {
t->right = NULL;
}
return t;
}
TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
if(inorder.size() == 0||postorder.size() == 0) return NULL;
return f(inorder,0,inorder.size()-1,postorder,0,postorder.size()-1);
}
};