LeetCode Construct Binary Tree from Preorder and Inorder Traversal

Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree.

Note:
You may assume that duplicates do not exist in the tree.

一个小小的下标没搞好，居然要浪费差不多一个小时，心痛啊。

中序遍历序列和后序遍历序列的偏移位置都需要仔细设计好。

class Solution {
public:
	TreeNode *buildTree(vector
  
    &preorder, vector
   
     &inorder) { return conTree(preorder, inorder, 0, preorder.size()-1, 0, inorder.size()-1); } TreeNode *conTree(vector
    
      &preo, vector
     
       &ino, int prel, int prer, int inl, int inr) { if (prel > prer) return NULL; TreeNode *t = new TreeNode(preo[prel]); auto it = find(ino.begin()+inl, ino.begin()+inr+1, preo[prel]); int offset = it-ino.begin()-inl; //注意：切记，下标如何定位要清楚，是offset还是绝对位置不能搞混了！ t->left = conTree(preo, ino, prel+1, prel+offset, inl, inl+offset-1); t->right = conTree(preo, ino, prel+offset+1, prer, inl+offset+1, inr); return t; } };