LeetCode 530. Minimum Absolute Difference in BST

530. Minimum Absolute Difference in BST

Description

Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes.

 Example:

Input:

   1
    \
     3
    /
   2

Output:
1

Explanation:
The minimum absolute difference is 1, which is the difference between 2 and 1 (or between 2 and 3).

Solution

• 題意即返回一棵二叉搜索樹上任意兩個節點之間的最小絕對值.
• 我們可以利用二叉搜索樹的性質，中序遍歷之後是有序數組，然後在有序數組中獲得最小絕對值是很容易的，只需要線性遍歷一遍即可，代碼如下：

class Solution {
public:
    vector<int> t;
    void travel(TreeNode *root) {
        if (!root) return;
        travel(root->left);
        t.push_back(root->val);
        travel(root->right);
        return ;
    }
    int getMinimumDifference(TreeNode* root) {
        travel(root);
        int minvalue = 100000;
        for (int i = 1;i < t.size();i++) {
            minvalue = min(minvalue,t[i] - t[i - 1]);
        }
        return minvalue;
    }
};