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LeetCode_236.java
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LeetCode_236.java
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import java.util.LinkedList;
import java.util.Queue;
public class LeetCode_236 {
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) {
Queue<TreeNode> queue = new LinkedList<>();
TreeNode ans = new TreeNode(-1);
queue.add(root);
while (!queue.isEmpty()) {
int len = queue.size();
for (int i = 0; i < len; i++) {
TreeNode node = queue.poll();
if (DFS(node, p, q) == 2) {
ans.val = node.val;
// System.out.println("aaa:" + ans.val);
}
if (node.left != null)
queue.add(node.left);
if (node.right != null)
queue.add(node.right);
}
}
return ans;
}
public int DFS(TreeNode node, TreeNode p, TreeNode q) {
int cnt = 0;
if (node == null) {
return 0;
}
if (node.val == p.val || node.val == q.val) {
cnt++;
}
return cnt + DFS(node.left, p, q) + DFS(node.right, p, q);
}
}
}