題目大意:把二叉搜索樹轉化成累加樹,使得每個節點的值是原來的節點值加上所有大於它的節點值之和
分析:題意轉化成=>從右往左中序遍歷,並且在遍歷過程中記錄前一個訪問節點的值
代碼:
/**
* 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 {
TreeNode* pre = NULL;
public:
TreeNode* convertBST(TreeNode* root) {
if(!root) return NULL;
convertBST(root->right);
if(pre) root->val += pre->val;
pre = root;
convertBST(root->left);
return root;
}
};