Create 9 October Postorder Traversal (#903)

Author: Chayandas07

9 October Postorder Traversal

@@ -0,0 +1,16 @@
+
+class Solution {
+    void post(Node* root, vector<int>& ans){
+        if (!root) return;
+        post(root->left, ans);
+        post(root->right, ans);
+        ans.push_back(root->data);
+    }
+  public:
+    vector<int> postOrder(Node* root) {
+        // code here
+        vector<int> ans;
+        post(root, ans);
+        return ans;
+    }
+};