题目：

代码（首刷看解析 2024年1月31日）：

class Solution {
public:int getMinimumDifference(TreeNode* root) {vector<int> vec;Helper(root, vec);int min_val = INT_MAX;for (int i = 0; i < vec.size() - 1; ++i) {min_val = min(min_val, vec[i + 1] - vec[i]);}return min_val;}void Helper(TreeNode* cur, vector<int>& vec) {if (!cur) return;Helper(cur->left, vec);vec.emplace_back(cur->val);Helper(cur->right,vec);}
};

代码（首刷看解析 2024年1月31日）

class Solution {
private:int min_val = INT_MAX;TreeNode* pre = nullptr;
public:int getMinimumDifference(TreeNode* root) {Helper(root);return min_val;}void Helper(TreeNode* cur) {if (cur == nullptr) return;Helper(cur->left);if (pre != nullptr) {min_val = min(min_val, cur->val - pre->val);}pre = cur;Helper(cur->right);}
};