LEETCODE: Construct Binary Tree from Inorder and Postorder Traversal

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于 2014-12-30 22:42:50 发布

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文章标签： LEETCODE 算法二叉树递归遍历

本文链接：https://blog.youkuaiyun.com/anyicheng2015/article/details/42276533

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本文详细介绍了如何通过中序遍历和后序遍历构造二叉树的方法，采用递归实现，确保理解深入。

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

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

递归！

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode *buildTree(vector<int>::iterator posbegin, vector<int>::iterator posend, 
                        vector<int>::iterator inbegin, vector<int>::iterator inend) {
        if(posbegin == posend) return NULL;
        TreeNode *root = new TreeNode(*(posend - 1));
        auto pos = find(inbegin, inend, *(posend - 1));
        int length = pos - inbegin;
        root->left = buildTree(posbegin, posbegin + length, inbegin, inbegin + length);
        root->right = buildTree(posbegin + length, posend - 1, inbegin + length + 1, inend);  
        return root;
    }
    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
        return buildTree(postorder.begin(), postorder.end(), inorder.begin(), inorder.end());
    }
};