[leetcode] 538. Convert BST to Greater Tree
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Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.
Example:
Input: The root of a Binary Search Tree like this: 5 / \ 2 13Output: The root of a Greater Tree like this: 18 / \ 20 13
这道题是“转化”二叉树,题目难度为Medium。
如果题目变为:将所有节点值转化为当前值加上比它小的节点值,相信会简单很多。我们知道中序遍历BST时节点值呈递增状态,所有比当前节点值小的节点在中序遍历时都在它之前,因此通过中序遍历即可顺利“转化”二叉树。
题目要求将所有节点值转化为当前值加上比它大的节点值,在中序遍历时只需要先遍历节点的右子树即可。具体代码:
class Solution { void inOrder(TreeNode* n, int& curSum) { if(n->right) inOrder(n->right, curSum); curSum += n->val; n->val = curSum; if(n->left) inOrder(n->left, curSum); }public: TreeNode* convertBST(TreeNode* root) { if(!root) return NULL; int curSum = 0; inOrder(root, curSum); return root; }};
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- Leetcode-538. Convert BST to Greater Tree
- 【LeetCode】538. Convert BST to Greater Tree
- [leetcode] 538. Convert BST to Greater Tree
- Leetcode 538. Convert BST to Greater Tree
- leetcode 538. Convert BST to Greater Tree
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- leetcode 538. Convert BST to Greater Tree
- [leetcode]538. Convert BST to Greater Tree
- LeetCode 538. Convert BST to Greater Tree
- leetcode 538. Convert BST to Greater Tree
- [LeetCode] 538. Convert BST to Greater Tree
- [LeetCode]538. Convert BST to Greater Tree
- LeetCode 538. Convert BST to Greater Tree
- leetcode 538. Convert BST to Greater Tree
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