package jjn.carl.binary_tree;
import commons.BinaryTreeHelper;
import commons.TreeNode;
import java.util.*;
/**
 * @author Jiang Jining
 * @since 2023-07-12 23:40
 */
public class LeetCode102 {
    public List<List<Integer>> levelOrder(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        List<List<Integer>> result = new ArrayList<>();
        if (root == null) {
            return result;
        }
        queue.offer(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            List<Integer> level = new ArrayList<>();
            for (int i = 0; i < size; i++) {
                TreeNode poll = queue.poll();
                if (poll == null) {
                    continue;
                }
                level.add(poll.val);
                if (poll.left != null) {
                    queue.offer(poll.left);
                }
                if (poll.right != null) {
                    queue.offer(poll.right);
                }
            }
            result.add(level);
        }
        return result;
    }
    public static void main(String[] args) {
        List<Integer> input = new ArrayList<>();
        input.addAll(List.of(3, 9, 20));
        input.add(null);
        input.add(null);
        input.add(15);
        input.add(7);
        TreeNode root = BinaryTreeHelper.buildTree(input);
        List<List<Integer>> levelledOrder = new LeetCode102().levelOrder(root);
        System.out.println("levelledOrder = " + levelledOrder);
    }
}

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode invertTree(TreeNode root) {
        if (root == null) {
            return root;
        }
        TreeNode left = root.left;
        TreeNode right = root.right;
        root.left = invertTree(right);
        root.right = invertTree(left);
        return root;
    }
}

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
     public boolean isSymmetric(TreeNode root) {
        if (root == null) {
            return true;
        }
        return isSymmetricPairs(root.left, root.right);
    }
    private boolean isSymmetricPairs(TreeNode left, TreeNode right) {
        if (left == null && right == null) {
            return true;
        }
        if (left == null || right == null) {
            return false;
        }
        if (left.val != right.val) {
            return false;
        }
        return isSymmetricPairs(left.left, right.right) && isSymmetricPairs(left.right, right.left);
    }
}