leetcode-solution/Java/Q617MergeBinaryTrees.java at main · b-knd/leetcode-solution · GitHub

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/*
@b-knd (jingru) on 06 August 2022 10:47:00
*/

/**
 * 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 {
    TreeNode head;

    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
        //one of the trees is empty (no more nodes
        if(root1 == null){
            return root2;
        } if(root2 == null){
            return root1;
        }

        root1.val += root2.val;
        root1.left = mergeTrees(root1.left, root2.left);
        root1.right = mergeTrees(root1.right, root2.right);
        return root1;
    }
}

//Runtime: 1 ms, faster than 81.09% of Java online submissions for Merge Two Binary Trees.
//Memory Usage: 50.3 MB, less than 80.43% of Java online submissions for Merge Two Binary Trees.