LeetCode 530. Minimum Absolute Difference in BST (二叉搜索树中最小绝对差)
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.
题目标签:Binary Search Tree
这道题目给了我们一个二叉搜索树,其特性为 左 < 根 < 右。让我们找到树中最小的绝对差值,可以存在任意两点中。如果看到二叉搜索树,一定要条件反射性的想起用 inOrder traverse,所有的值是从小到大的排序。这样就很容易找到最小的绝对差了,对于每一个点,和之前那个点比较一下,遍历完树,就可以找到最小的差值。
Java Solution:
Runtime beats 77.33%
完成日期:07/10/2017
关键词:Binary Search Tree
关键点:利用 inOrder traverse 遍历树,所有点的值排序为从小到大
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * int val; 5 * TreeNode left; 6 * TreeNode right; 7 * TreeNode(int x) { val = x; } 8 * } 9 */ 10 public class Solution 11 { 12 int minDiff = Integer.MAX_VALUE; 13 TreeNode preNode = null; 14 15 public int getMinimumDifference(TreeNode root) 16 { 17 inOrder(root); 18 return minDiff; 19 } 20 21 public void inOrder(TreeNode node) 22 { 23 if(node == null) 24 return; 25 26 inOrder(node.left); 27 28 // get the diff between preNode and node 29 if(preNode != null) // because the first time preNode is null 30 minDiff = Math.min(minDiff, Math.abs(node.val - preNode.val)); 31 32 preNode = node; 33 34 inOrder(node.right); 35 } 36 }
参考资料:
http://www.cnblogs.com/grandyang/p/6540165.html
LeetCode 算法题目列表 - LeetCode Algorithms Questions List