Data Structures (#44)

* added singly linked list in c++

* changed .gitignore to ignore binary files for c++ and java

* changed .gitignore to ignore binary files for c++ and java

* i changed as per review , method names in SinglyLinkedList and folder name

* i changed directory name as per convention

.gitignore

@@ -1,8 +1,12 @@
-# OS generated files 
+# OS generated files
 .DS_Store
 .DS_Store?
 ._*
 .Spotlight-V100
 .Trashes
 ehthumbs.db
-Thumbs.db
+Thumbs.db
+
+# binary files
+*.out
+*.class

linked-lists/README.md

@@ -0,0 +1,5 @@
+# Linked Lists
+
+### c or c++
+
+1. [Singly Linked List](c-or-cpp/SinglyLinkedList.cpp)

linked-lists/c-or-cpp/SinglyLinkedList.cpp

@@ -0,0 +1,79 @@
+#include <iostream>
+
+template <typename T>
+class Node {
+    public:
+        T data;
+        Node *next;
+
+        Node(T data)
+            : data(data) , next(nullptr) {};
+};
+
+template <typename T>
+class SinglyLinkedList {
+    private:
+        Node<T>* head;
+
+    public:
+        SinglyLinkedList()
+            : head(nullptr){}
+
+        void insertAtHead(T data) {
+            Node<T> *temp = new Node<T>(data);
+
+            // if head is not pointing to anything then simply point to new node
+            if(this->head == nullptr) {
+                this->head = temp;
+                return;
+            }
+
+            // if head is already point at some node
+            // first make new node points to head address
+            temp->next = this->head;
+            // change head point to new node
+            this->head = temp;
+        }
+
+        T removeAtHead() {
+            // if list is empty we can't remove node
+            if(this->head == nullptr) {
+                std::cout<<"List is Empty"<<std::endl;
+                exit(1);
+            }
+
+            // save data of node where head is pointed
+            T data = this->head->data;
+            // save temp pointer to free the memory
+            Node<T>* temp_ptr = this->head;
+            this->head = this->head->next;
+
+            // free memory
+            delete temp_ptr;
+            return data;
+        }
+
+        void printList() const {
+            if(this->head == nullptr) {
+                std::cout<<"List is Empty"<<std::endl;
+            } else {
+                Node<T> *itr = this->head;
+                // iterate through list until itr reach to nullptr and print data
+                while(itr != nullptr) {
+                    std::cout<<itr->data<<" ";
+                    itr = itr->next;
+                }
+                std::cout<<std::endl;
+            }
+        }
+};
+
+int main() {
+    SinglyLinkedList<int> l;
+    l.insertAtHead(1);
+    l.insertAtHead(2);
+    l.insertAtHead(3);
+    l.removeAtHead();
+    l.printList();
+    return 0;
+}