1038. Binary Search Tree to Greater Sum Tree

[namespace-io]

太久没做题了 没手感居然写了半小时

/**
 * 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:
    int prev = 0;
    
    TreeNode* bstToGst(TreeNode* cur) {
 
        if(cur == nullptr) return nullptr;
        auto root = new TreeNode(0);
        root->right = bstToGst(cur->right);
        root->val = cur->val + prev;
        prev = root->val;
        root->left = bstToGst(cur->left);
 
        return root;;
    }
};