Gives you the root node of a binary search tree, and returns the minimum difference between any two different values of the tree. 1: Input: root = [4,2,6,1,3] Output: //DFS Treenode Pre; //DFS Treenode Pre; int min = Integer.MAX_VALUE; public int minDiffInBST(TreeNode root) { dfs(root); return min; } public void dfs(TreeNode root){ if(root == null) return; dfs(root.left); if(pre ! = null) min = Math.min(min,root.val - pre.val); pre = root; dfs(root.right); }}