题目链接

层序遍历

/*** 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 mergeTrees(TreeNode root1, TreeNode root2) {if(root1 == null){return root2;}if(root2 == null){return root1;}Deque<TreeNode> queue = new LinkedList<TreeNode>();queue.offer(root1);queue.offer(root2);while(!queue.isEmpty()){TreeNode node1 = queue.poll();TreeNode node2 = queue.poll();node1.val += node2.val;if(node1.left != null && node2.left != null){queue.offer(node1.left);queue.offer(node2.left);}if(node1.right != null && node2.right != null){queue.offer(node1.right);queue.offer(node2.right);}if(node1.left == null && node2.left != null){node1.left = node2.left;}if(node1.right == null && node2.right != null){node1.right = node2.right;}}return root1;}
}