Package g0201_0300.s0236_lowest_common_ancestor_of_a_binary_tree

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    236 - Lowest Common Ancestor of a Binary Tree.

    Medium

    Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

    According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself ).”

    Example 1:

    Input: root = 3,5,1,6,2,0,8,null,null,7,4, p = 5, q = 1

    Output: 3

    Explanation: The LCA of nodes 5 and 1 is 3.

    Example 2:

    Input: root = 3,5,1,6,2,0,8,null,null,7,4, p = 5, q = 4

    Output: 5

    Explanation: The LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.

    Example 3:

    Input: root = 1,2, p = 1, q = 2

    Output: 1

    Constraints:

    • The number of nodes in the tree is in the range <code>2, 10<sup>5</sup></code>.

    • <code>-10<sup>9</sup><= Node.val <= 10<sup>9</sup></code>

    • All Node.val are unique.

    • p != q

    • p and q will exist in the tree.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q)

      • Methods inherited from class java.lang.Object

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