Create n-ary-tree-preorder-traversal.cpp

Author: kamyu104

C++/n-ary-tree-preorder-traversal.cpp

@@ -0,0 +1,40 @@
+// Time:  O(n)
+// Space: O(h)
+
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    vector<Node*> children;
+
+    Node() {}
+
+    Node(int _val, vector<Node*> _children) {
+        val = _val;
+        children = _children;
+    }
+};
+*/
+class Solution {
+public:
+    vector<int> preorder(Node* root) {
+        if (!root) {
+            return {};
+        }
+        vector<int> result;
+        vector<Node*> stack{root};
+        while (!stack.empty()) {
+            auto node = stack.back(); stack.pop_back();
+            result.emplace_back(node->val);
+            for (auto rit = node->children.rbegin();
+                 rit != node->children.rend();
+                 ++rit) {
+                if (*rit) {
+                    stack.emplace_back(*rit);
+                }
+            }
+        }
+        return result;
+    }
+};