<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://assets.leetcode.com/uploads/2021/02/05/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://assets.leetcode.com/uploads/2021/02/05/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>

class Solution {
 public:
  // Similar to 94. Binary Tree Inorder Traversal
  int getMinimumDifference(TreeNode* root) {
    int ans = INT_MAX;
    int prev = -1;
    stack<TreeNode*> stack;

    while (root != nullptr || !stack.empty()) {
      while (root != nullptr) {
        stack.push(root);
        root = root->left;
      }
      root = stack.top(), stack.pop();
      if (prev >= 0)
        ans = min(ans, root->val - prev);
      prev = root->val;
      root = root->right;
    }

    return ans;
  }
};
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