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;    }};

/** * 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;    }};