MergeTrees617.java

package Leetcode;

public class MergeTrees617 {
  /*Method: Iteration, Time: O(min(N1, N2)), Space:O(min(N1, N2))**/
  public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
    if(root1 == null && root2 == null) {
      return null;
    }
    if(root1 == null || root2 == null) {
      return root1 == null ? root2: root1;
    }
    TreeNode root = new TreeNode(root1.val + root2.val);
    root.left = mergeTrees(root1.left, root2.left);
    root.right = mergeTrees(root1.right, root2.right);
    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;
    }
  }

}