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 13 Output: The root of a Greater Tree like this: 18 / \ 20 13
A:
-------------利用 BST -----------/** * 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* convertBST(TreeNode* root) { int curSum =0; traversal(root, curSum); return root; } private: void traversal(TreeNode * root, int & S) { if(not root) return; traversal(root->right, S); root->val += S; S = root->val; traversal(root->left, S); } };
Mistakes:
root->val += S
S+= root->val 这两句是错误的, 需要利用tmp来保存临时值
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