2017/11/7 Leetcode 日记
669. Trim a Binary Search Tree
Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.
(修改二叉搜索树，将[L, R]外的节点删除)
/**
* 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* trimBST(TreeNode* root, int L, int R) {
if(root == NULL) return NULL;
if(root->val < L) return trimBST(root->right, L, R);
if(root->val > R) return trimBST(root->left, L, R); root->left = trimBST(root->left, L, R);
root->right = trimBST(root->right, L, R);
return root;
}
};
c++ 未释放内存
/**
* 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* trimBST(TreeNode* root, int L, int R, bool top = true) {
if(root == NULL) return NULL; root->left = trimBST(root->left, L, R, false);
root->right = trimBST(root->right, L, R, false); if(root->val >= L && root->val <= R) return root;
auto result = root->val < L ? root->right : root->left;
if(!top) delete root;
return result;
}
};
c++ 释放内存