solved: 617

Author: ryoppippi

code/617.merge-two-binary-trees.ts

@@ -0,0 +1,42 @@
+class TreeNode {
+  val: number;
+  left: TreeNode | null;
+  right: TreeNode | null;
+  constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.left = left === undefined ? null : left;
+    this.right = right === undefined ? null : right;
+  }
+}
+
+// @leet start
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function mergeTrees(
+  root1: TreeNode | null,
+  root2: TreeNode | null,
+): TreeNode | null {
+  if (root1 == null && root2 == null) return null; // if both the roots are null, return null
+  if (root1 == null || root2 == null) return root1 ?? root2; // if either of the root is null, return the other root
+
+  root1.val += root2.val; // merge the values of the roots
+
+  root1.left = mergeTrees(root1.left, root2.left); // recursively merge the left subtrees
+  root1.right = mergeTrees(root1.right, root2.right); // recursively merge the right subtrees
+
+  return root1; // return the merged tree
+}
+// @leet end
+