LeetCode - 106. Construct Binary Tree from Inorder and Postorder Traversal

virgilshi

于 2019-07-16 18:43:52 发布

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分类专栏： LeetCode

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本文详细解析了LeetCode上的106题：通过中序和后序遍历构建二叉树的问题。提供了清晰的解题思路，并附带完整的C++实现代码。通过对105题的借鉴，使得解决此题变得更为直观。

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题目

LeetCode - 106. Construct Binary Tree from Inorder and Postorder Traversal

题目链接

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

参考博客

解题思路

解题思路可以参考105那题。

解题源码

/**
 * 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:
    TreeNode* build(vector<int>& inorder, vector<int>& postorder, int start1, int end1, int start2, int end2){
        if (start1 > end1 || start2 > end2) return nullptr;
        TreeNode* root = new TreeNode(postorder[end2]);
        int index = end1;
        while (index >= start1 && postorder[end2] != inorder[index]) index--;
        root->left = build(inorder, postorder, start1, index - 1, start2, start2 + (index - start1) -1);
        root->right = build(inorder, postorder, index + 1, end1, start2 + index - start1, end2 - 1);
        
        return root;
    }
    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
        int len = postorder.size();
        return build(inorder, postorder, 0, len - 1, 0, len - 1);
    }
};