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MinimumDistanceBetweenBSTNodes783.java
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72 lines (65 loc) · 2.14 KB
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/**
* Given a Binary Search Tree (BST) with the root node root, return the minimum
* difference between the values of any two different nodes in the tree.
*
* Example :
*
* Input: root = [4,2,6,1,3,null,null]
* Output: 1
* Explanation:
* Note that root is a TreeNode object, not an array.
*
* The given tree [4,2,6,1,3,null,null] is represented by the following diagram:
*
* 4
* / \
* 2 6
* / \
* 1 3
*
* while the minimum difference in this tree is 1, it occurs between node 1 and
* node 2, also between node 3 and node 2.
*
* Note:
* The size of the BST will be between 2 and 100.
* The BST is always valid, each node's value is an integer, and each node's
* value is different.
*/
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class MinimumDistanceBetweenBSTNodes783 {
public int minDiffInBST(TreeNode root) {
int[] res = new int[]{Integer.MAX_VALUE};
minDiffInBST(root, new LinkedList<>(), res);
return res[0];
}
public void minDiffInBST(TreeNode root, LinkedList<Integer> list, int[] res) {
if (root.left != null) minDiffInBST(root.left, list, res);
if (!list.isEmpty() && root.val - list.getLast() < res[0]) {
res[0] = root.val - list.getLast();
}
list.add(root.val);
if (root.right != null) minDiffInBST(root.right, list, res);
}
public int minDiffInBST2(TreeNode root) {
int[] res = new int[]{Integer.MAX_VALUE};
Integer[] pre = new Integer[]{null};
minDiffInBST2(root, new LinkedList<>(), pre, res);
return res[0];
}
public void minDiffInBST2(TreeNode root, LinkedList<Integer> list, Integer[] pre, int[] res) {
if (root.left != null) minDiffInBST2(root.left, list, pre, res);
if (pre[0] != null && root.val - pre[0] < res[0]) {
res[0] = root.val - pre[0];
}
pre[0] = root.val;
if (root.right != null) minDiffInBST2(root.right, list, pre, res);
}
}