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450.delete-node-in-a-bst.cpp
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93 lines (87 loc) · 2.55 KB
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// Tag: Tree, Binary Search Tree, Binary Tree
// Time: O(H)
// Space: O(H)
// Ref: -
// Note: Delete
// 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.
//
//
// Example 1:
//
//
// Input: root = [5,3,6,2,4,null,7], key = 3
// Output: [5,4,6,2,null,null,7]
// Explanation: Given 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 above BST.
// Please notice that another valid answer is [5,2,6,null,4,null,7] and it's also accepted.
//
//
// Example 2:
//
// Input: root = [5,3,6,2,4,null,7], key = 0
// Output: [5,3,6,2,4,null,7]
// Explanation: The tree does not contain a node with value = 0.
//
// Example 3:
//
// Input: root = [], key = 0
// Output: []
//
//
// Constraints:
//
// The number of nodes in the tree is in the range [0, 104].
// -105 <= Node.val <= 105
// Each node has a unique value.
// root is a valid binary search tree.
// -105 <= key <= 105
//
//
// Follow up: Could you solve it with time complexity O(height of tree)?
//
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
TreeNode* deleteNode(TreeNode* root, int key) {
if (!root) {
return nullptr;
}
if (root->val < key) {
root->right = deleteNode(root->right, key);
} else if (root->val > key) {
root->left = deleteNode(root->left, key);
} else {
if (!root->left) {
TreeNode* temp = root->right;
delete root;
return temp;
}
if (!root->right) {
TreeNode* temp = root->left;
delete root;
return temp;
}
TreeNode *rigth_min = root->right;
while (rigth_min->left) {
rigth_min = rigth_min->left;
}
root->val = rigth_min->val;
root->right = deleteNode(root->right, root->val);
}
return root;
}
};