LCR 054. 把二叉搜索树转换为累加树

使用后序遍历即可

class Solution {
public:
    TreeNode* convertBST(TreeNode* root) {
        int temp = 0;
        dfs(root,temp);
        return root;
    }

    void dfs(TreeNode* root,int &temp){
        if(!root){
            return ;
        }
        dfs(root->right,temp);
        temp += root->val;
        root->val = temp;
        dfs(root->left,temp);
    }
};