[이총명] Day16

leetcode2/1easy/이총명/Q617.java

@@ -0,0 +1,40 @@
+/**
+ * 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) {
+        // 둘 다 null이면 종료
+        if(root1 == null) return root2;
+        if(root2 == null) return root1;
+
+        // 두 노드 중 하나라도 null이면 0으로 간주해서 값을 더함.
+        int val1 = (root1 != null) ? root1.val : 0;
+        int val2 = (root2 != null) ? root2.val : 0;
+
+        TreeNode newNode = new TreeNode(val1 + val2);
+
+        newNode.left = mergeTrees(
+            (root1 != null) ? root1.left : null,
+            (root2 != null) ? root2.left : null
+        );
+
+        newNode.right = mergeTrees(
+            (root1 != null) ? root1.right : null,
+            (root2 != null) ? root2.right : null
+        );
+
+        return newNode;
+    }
+}