g0601_0700.s0671_second_minimum_node_in_a_binary_tree

Class Solution

java.lang.Object

g0601_0700.s0671_second_minimum_node_in_a_binary_tree.Solution

public class Solution
extends Object

671 - Second Minimum Node In a Binary Tree.

Easy

Given a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactly two or zero sub-node. If the node has two sub-nodes, then this node’s value is the smaller value among its two sub-nodes. More formally, the property root.val = min(root.left.val, root.right.val) always holds.

Given such a binary tree, you need to output the second minimum value in the set made of all the nodes’ value in the whole tree.

If no such second minimum value exists, output -1 instead.

Example 1:

Input: root = [2,2,5,null,null,5,7]

Output: 5

Explanation: The smallest value is 2, the second smallest value is 5.

Example 2:

Input: root = [2,2,2]

Output: -1

Explanation: The smallest value is 2, but there isn’t any second smallest value.

Constraints:

• The number of nodes in the tree is in the range [1, 25].
• 1 <= Node.val <= 231 - 1
• root.val == min(root.left.val, root.right.val) for each internal node of the tree.

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	findSecondMinimumValue(TreeNode root)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

findSecondMinimumValue

public int findSecondMinimumValue(TreeNode root)