Added Question in Love Babbar DSA Sheet

Love Babbar DSA Sheet/2. Matrix/README.md

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+# Coming soon

Love Babbar DSA Sheet/3. String/README.md

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+# Coming soon

Love Babbar DSA Sheet/4. Searching & Sorting/README.md

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+# Coming soon

Love Babbar DSA Sheet/5. LinkedList/README.md

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+# Coming soon

Love Babbar DSA Sheet/6. Binary Trees/2. Reverse Level Order Traversal/code.cpp

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+#include <bits/stdc++.h>
+using namespace std;
+
+/*Ques - Given a binary tree of size N, find its reverse level order traversal. ie- the traversal must begin from the last level.
+
+Input - 1 3 2 -1 -1 -1 -1
+
+Output - 3 2 1
+*/
+
+class Node{
+public:
+  int data;
+  Node *left;
+  Node *right;
+
+  Node(int data){
+    this->data = data;
+    left = right = NULL;
+  }
+
+  ~Node(){
+    delete left;
+    delete right;
+  }
+};
+
+Node *buildBinaryTree(){
+  int rootData;
+  cout << "Enter root data - ";
+  cin >> rootData;
+
+  Node *root = new Node(rootData);
+
+  queue<Node *> pendingNodes;
+  pendingNodes.push(root);
+
+  while (!pendingNodes.empty()){
+    Node *front = pendingNodes.front();
+    pendingNodes.pop();
+
+    int leftData;
+    cout << "Enter Left Child of " << front->data << "\n";
+    cin >> leftData;
+
+    if (leftData != -1){
+      Node *leftChild = new Node(leftData);
+      front->left = leftChild;
+      pendingNodes.push(leftChild);
+    }
+
+    int rightData;
+    cout << "Enter Right Child of " << front->data << "\n";
+    cin >> rightData;
+
+    if (rightData != -1){
+      Node *rightChild = new Node(rightData);
+      front->right = rightChild;
+      pendingNodes.push(rightChild);
+    }
+  }
+
+  return root;
+}
+
+vector<int> reverseLevelOrder(Node *root){
+  vector<int> ans;
+  stack<Node *> s;
+  queue<Node *> q;
+  q.push(root);
+
+  while (!q.empty()){
+    Node *front = q.front();
+    q.pop();
+    s.push(front);
+
+    if (front->right)
+      q.push(front->right);
+
+    if (front->left)
+      q.push(front->left);
+  }
+
+  while (!s.empty()){
+    Node *temp = s.top();
+    ans.push_back(temp->data);
+    s.pop();
+  }
+
+  return ans;
+}
+
+int main(){
+
+  Node *root = buildBinaryTree();
+
+  vector<int> ans = reverseLevelOrder(root);
+
+  for(int e : ans)
+    cout << e << " ";
+
+  delete root;
+  return 0;
+}