Package 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 java.lang.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
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    findSecondMinimumValue(TreeNode root)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • findSecondMinimumValue

      public int findSecondMinimumValue(TreeNode root)