add

Author: kamyu104

C++/add-one-row-to-tree.cpp

@@ -0,0 +1,28 @@
+// Time:  O(n)
+// Space: O(h)
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* addOneRow(TreeNode* root, int v, int d) {
+        if (d == 0 || d == 1) {
+            auto node = new TreeNode(v);
+            (d == 1 ? node->left : node->right) = root;
+            return node;
+        }
+        if (root && d >= 2) {
+            root->left  = addOneRow(root->left,  v, d > 2 ? d - 1 : 1);
+            root->right = addOneRow(root->right, v, d > 2 ? d - 1 : 0);
+        }
+        return root;
+    }
+};
+