my-leetcode-logs-20230719

669. 修剪二叉搜索树（递归实现，C++）

/**
 * 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* trimBST(TreeNode* root, int low, int high) {
        //迭代实现
        if(root == NULL){
            return NULL;
        }

        //当前结点的值小于low，那么遍历root的right右子树
        if(root->val < low){
            TreeNode* node = trimBST(root->right, low, high);
            return node;
        }

        //当前结点的值大于high，那么遍历root的左子树
        if(root->val > high){
            TreeNode* node = trimBST(root->left, low, high);
            return node;
        }

        root->left = trimBST(root->left, low, high);
        root->right = trimBST(root->right, low, high);
        return root;
    }
};

669. 修剪二叉搜索树（迭代法实现，C++）

/**
 * 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* trimBST(TreeNode* root, int low, int high) {
        if(root == NULL){
            return NULL;
        }

        //处理根结点，将新树的root结点调节到low,hight之间
        while(root != NULL && (root->val < low || root->val > high)){
            if(root->val < low){
                root = root->right;
            }else{
                root = root->left;
            }
        }

        //继续处理
        TreeNode* curr = root;
        while(curr != NULL){//处理左子树小于low的情况
            //循环找到左边界
            while(curr->left != NULL && curr->left->val < low){
                curr->left = curr->left->right;
            }
            //处理curr结点的
            curr = curr->left;
        }

        //处理root结点的右边，将大于high的结点删除掉
        curr = root;

        while(curr != NULL){
            while(curr->right != NULL && curr->right->val > high){
                curr->right = curr->right->left;
            }
            curr = curr->right;
        }

        return root;
    }
};