[LeetCode] Minimum Absolute Difference in BST

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).

Note: There are at least two nodes in this BST.

找出一个二叉树中任意两个节点的最小绝对值。利用二叉树中序遍历的性质，将二叉树按从小到大的顺序存储在一个数组中，然后遍历数组找出最小的绝对值。

class Solution {
public:
    vector<int> res;
    int getMinimumDifference(TreeNode* root) {
        inOrder(root);
        int minDiff = INT_MAX;
        for (int i = 1; i != res.size(); i++) {
            int tmp = res[i] - res[i - 1];
            minDiff = min(minDiff, tmp);
        }
        return minDiff;
    }
    void inOrder(TreeNode* root) {
        if (root == nullptr)
            return;
        inOrder(root->left);
        res.push_back(root->val);
        inOrder(root->right);
    }
};
// 19 ms