leetcode 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).” Given the following binary tree:? root =?[3,5,1,6,2,8,null,7,4] ? Cases: 1. currentNode is null or p or q,return currentNode; 2.?leftChild return a tree_node and rightChild return a tree_node,return currentNode 3. leftChild return a tree_node m and rightChild return null: ? ? ? ? return m 4. rightChild return a tree_node m and leftChild return null: ? ? ? ? return m /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public TreeNode lowestCommonAncestor(TreeNode root,TreeNode p,TreeNode q) { if(root==null||root==p||root==q) return root; TreeNode left= lowestCommonAncestor(root.left,p,q); TreeNode right= lowestCommonAncestor(root.right,q); if(left!=null &&right!=null) return root; else if(left!=null&&right==null){ return left; } else{ return right; } } } (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |