Minimum Absolute Difference in BST
<p>Given the <code>root</code> of a Binary Search Tree (BST), return <em>the minimum absolute difference between the values of any two different nodes in the tree</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0500-0599/0530.Minimum%20Absolute%20Difference%20in%20BST/images/bst1.jpg" style="width: 292px; height: 301px;" />
<pre>
<strong>Input:</strong> root = [4,2,6,1,3]
<strong>Output:</strong> 1
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0500-0599/0530.Minimum%20Absolute%20Difference%20in%20BST/images/bst2.jpg" style="width: 282px; height: 301px;" />
<pre>
<strong>Input:</strong> root = [1,0,48,null,null,12,49]
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[2, 10<sup>4</sup>]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Note:</strong> This question is the same as 783: <a href="https://leetcode.com/problems/minimum-distance-between-bst-nodes/" target="_blank">https://leetcode.com/problems/minimum-distance-between-bst-nodes/</a></p>
Tree; Depth-First Search; Breadth-First Search; Binary Search Tree; Binary Tree
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func getMinimumDifference(root *TreeNode) int {
	const inf int = 1 << 30
	ans, pre := inf, -inf
	var dfs func(*TreeNode)
	dfs = func(root *TreeNode) {
		if root == nil {
			return
		}
		dfs(root.Left)
		ans = min(ans, root.Val-pre)
		pre = root.Val
		dfs(root.Right)
	}
	dfs(root)
	return ans
}