617. Merge Two Binary Trees

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {
      
      if(t1 == null && t2 == null) return null;
      if(t1 == null) return t2;
      if(t2 == null) return t1;

      TreeNode mergedTree = new TreeNode(t1.val + t2.val);
      mergedTree.left = mergeTrees(t1.left, t2.left);
      mergedTree.right = mergeTrees(t1.right, t2.right);

      return mergedTree;
    }
}