技術標籤：遞迴二叉樹leetcode

實際上還是中序遍歷，只是從右邊開始遍歷

class Solution {
public:

    int s=0;
    TreeNode* convertBST(TreeNode* root) {
        if(!root)
        return NULL;
        convertBST(root->right);
        s+=root->val;
        root->val=s;
        convertBST(root->left); 
        return root;
 

    }
};

用迭代也做了下

class Solution {
public:
    TreeNode* bstToGst(TreeNode* root) {
        TreeNode* pmove=root;
        stack<TreeNode*> s; 
        int cal=0;
        while(!s.empty()||pmove)
        {
            while(pmove)
            {s.push(pmove);
            pmove=pmove->right;}
            pmove=
 
s.top();
            s.pop();
            cal+=pmove->val;
            pmove->val=cal;
            pmove=pmove->left;
        }
        return root;
    }
};