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Main.java
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Main.java
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package com.company;
import java.util.ArrayDeque;
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
public class Main {
public static void main(String[] args) {
// write your code here
}
boolean found;
public TreeNode lowestCommonAncestor_dfs(TreeNode root, TreeNode p, TreeNode q) {
ArrayDeque<TreeNode> pAncestors = new ArrayDeque<>();
ArrayDeque<TreeNode> qAncestors = new ArrayDeque<>();
dfs(root, p, pAncestors);
found = false;
dfs(root, q, qAncestors);
while (pAncestors.size() > qAncestors.size()) pAncestors.poll();
while (qAncestors.size() > pAncestors.size()) qAncestors.poll();
while (!pAncestors.isEmpty() && !qAncestors.isEmpty()){
if (pAncestors.peek() == qAncestors.peek()) return pAncestors.peek();
pAncestors.poll();
qAncestors.poll();
}
return root;
}
public void dfs(TreeNode node, TreeNode p, ArrayDeque<TreeNode> ancestors){
if(node == null || found) return;
if(node == p) found = true;
if(node.val > p.val) dfs(node.left, p, ancestors);
else dfs(node.right, p, ancestors);
if(found) ancestors.offer(node);
}
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if(root == null) return null;
if(p.val < root.val && q.val < root.val) return lowestCommonAncestor(root.left, p, q);
else if(p.val > root.val && q.val > root.val) return lowestCommonAncestor(root.right, p, q);
return root;
}
}