java: add «623. Add One Row to Tree»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/add-one-row-to-tree.java

@@ -0,0 +1,35 @@
+class Solution {
+  private enum Side {
+    Left,
+    Right
+  }
+
+  private TreeNode addOneRow(int depth, int val, TreeNode node, int currentDepth, Side s) {
+    if (depth == currentDepth) {
+      var newRoot = new TreeNode(val);
+      switch (s) {
+        case Left:
+          newRoot.left = node;
+          break;
+        case Right:
+          newRoot.right = node;
+          break;
+      }
+
+      return newRoot;
+    }
+
+    if (node == null) {
+      return node;
+    }
+
+    node.left = addOneRow(depth, val, node.left, currentDepth + 1, Side.Left);
+    node.right = addOneRow(depth, val, node.right, currentDepth + 1, Side.Right);
+
+    return node;
+  }
+
+  public TreeNode addOneRow(TreeNode root, int val, int depth) {
+    return addOneRow(depth, val, root, 1, Side.Left);
+  }
+}