Day33: [LeetCode中等] 106. 从中序与后序遍历序列构造二叉树

题源：

来自leetcode题库：

https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/

代码：

dirty code凑合看吧

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int root,Len;
    TreeNode* f(vector<int>& inorder, vector<int>& postorder,int left,int right){
        if(left>right) return NULL;
        int x=postorder[root--];
        TreeNode* p=new TreeNode(x);
        int i;
        for(i=0;i<Len;i++){
            if(inorder[i]==x) break;
        }
        p->right=f(inorder,postorder,i+1,right);
        p->left=f(inorder,postorder,left,i-1);
        return p;
    }
    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
       Len=inorder.size();
       if(Len==0) return NULL;
       root=Len-1;
       return f(inorder,postorder,0,Len-1);
    }
};