LeetCode
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Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.
Basically, the deletion can be divided into two stages:
- Search for a node to remove.
- If the node is found, delete the node.
Note: Time complexity should be O(height of tree).
Example:
root = [5,3,6,2,4,null,7]key = 3 5 / \ 3 6 / \ \2 4 7Given key to delete is 3. So we find the node with value 3 and delete it.One valid answer is [5,4,6,2,null,null,7], shown in the following BST. 5 / \ 4 6 / \2 7Another valid answer is [5,2,6,null,4,null,7]. 5 / \ 2 6 \ \ 4 7
查找并删除BST中某个结点。
这道题,在我写了96行代码还在wa后,对你没看错,96行!我果断放弃了这个代码,围观评论区大神orzzzzzzz
然后发现自己蠢的没救了。。。为啥非要执着于把那个结点删除然后调个结点过来呢,咱就不能直接改变结点值么然后再去删除想要调的那个结点么!!!震惊哭QAQ
递归简直是脑残人的救星,在不会做的情况下,我还是不要纠结非得写非递归吧,找块豆腐撞死算了。
一路搜索下去,沿途改变各个结点的左右状态,一直都搜索到key结点,找到key的右子树中值最小的结点,赋值给key,并删除这个结点。时间复杂度O(h)
/** * 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* deleteNode(TreeNode* root, int key) { if (!root) return root; if (key < root->val) root->left = deleteNode(root->left, key); else if (key > root->val) root->right = deleteNode(root->right, key); else { if (!root->left) return root->right; if (!root->right) return root->left; TreeNode* cur = finMin(root->right); root->val = cur->val; root->right = deleteNode(root->right, cur->val); } return root; } TreeNode* finMin(TreeNode* root) { while (root->left) root = root->left; return root; }};
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