LeetCode刷题（C++）——Construct Binary Tree from Inorder and Postorder Traversal（Normal）

题目描述

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

Note:

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

/**
* 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* buildTree(vector<int>& inorder, vector<int>& postorder) {
if (inorder.size() == 0 || postorder.size() == 0 || inorder.size() != postorder.size())
return NULL;
return dfs(inorder, 0, inorder.size() - 1, postorder, 0, postorder.size() - 1);
}

TreeNode* dfs(vector<int>&inorder, int l1, int r1, vector<int>& postorder, int l2, int r2)
{
if (l2 > r2)
return NULL;
if (l2 == r2)
return new TreeNode(postorder[r2]);
TreeNode* root = new TreeNode(postorder[r2]);
for (int i = 0; i < inorder.size();i++)
{
if (inorder[i] == postorder[r2])
{
root->left = dfs(inorder, l1, i - 1, postorder, l2, l2 + i - l1-1);
root->right = dfs(inorder, i + 1, r1, postorder, l2 + i - l1, r2 - 1);
return root;
}
}
return NULL;
}
};