Day10

144. Binary Tree Preorder Traversal/Solution.cs

@@ -0,0 +1,22 @@
+namespace _144._Binary_Tree_Preorder_Traversal;
+
+public class Solution
+{
+    public IList<int> PreorderTraversal(TreeNode root)
+    {
+        List<int> res = new List<int>();
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        if (root != null)
+            stack.Push(root);
+        while (stack.Count > 0)
+        {
+            TreeNode cur = stack.Pop();
+            if (cur.right != null)
+                stack.Push(cur.right);
+            if (cur.left != null)
+                stack.Push(cur.left);
+            res.Add(cur.val);
+        }
+        return res;
+    }
+}