/**
You are given two binary trees root1 and root2.
Imagine that when you put one of them to cover the other, some nodes of the
two trees are overlapped while the others are not. You need to merge the two trees
into a new binary tree. The merge rule is that if two nodes overlap, then sum
node values up as the new value of the merged node. Otherwise, the NOT null node
will be used as the node of the new tree.
Return the merged tree.
Note: The merging process must start from the root nodes of both trees.
Example 1:
Input: root1 = [1,3,2,5], root2 = [2,1,3,null,4,null,7]
Output: [3,4,5,5,4,null,7]
Example 2:
Input: root1 = [1], root2 = [1,2]
Output: [2,2]
Constraints:
The number of nodes in both trees is in the range [0, 2000].
-10⁴ <= Node.val <= 10⁴
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*/
//leetcode submit region begin(Prohibit modification and deletion)
/**
* 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;
} else if (root2 == null) {
return root1;
}
root1.val += root2.val;
if (root1.left != null) {
root1.left = mergeTrees(root1.left, root2.left);
} else if (root2.left != null) {
root1.left = root2.left;
}
if (root1.right != null) {
root1.right = mergeTrees(root1.right, root2.right);
} else if (root2.right != null) {
root1.right = root2.right;
}
return root1;
}
}
//leetcode submit region end(Prohibit modification and deletion)
