Create train_composition.cpp

cpp-exercises/train_composition.cpp

@@ -0,0 +1,182 @@
+#include <stdexcept>
+#include <iostream>
+#include <chrono>
+
+class Wagon
+{
+public:
+
+    int wagonID;
+    Wagon* to_the_left;
+    Wagon* to_the_right;
+
+    Wagon(int wagonID)
+    {
+        this->wagonID = wagonID;
+    }
+
+};
+
+class TrainComposition
+{
+
+private:
+    Wagon* left_wagon; // Leftmost and rightmost wagons
+    Wagon* right_wagon; 
+
+    int train_length = 0;
+
+    // If this is the first wagon added to the train
+    void initialise_train(int wagonID)
+    {
+        Wagon* wagon = new Wagon(wagonID);
+
+        this->left_wagon = wagon;
+        this->right_wagon = wagon;
+
+        this->train_length++;
+    }
+
+public:
+    void attachWagonFromLeft(int wagonId)
+    {
+        // Check if there is already a wagon on the train, if yes update the leftmost wagon
+        if(this->train_length == 0)
+        {
+            this->initialise_train(wagonId);
+        }
+        else
+        {
+            Wagon* old_left_wagon = this->left_wagon;
+            old_left_wagon->to_the_left = new Wagon(wagonId);
+            this->left_wagon = old_left_wagon->to_the_left;
+
+            // Update new leftmost wagon's properties
+            this->left_wagon->to_the_right = old_left_wagon;
+
+            this->train_length++; 
+        }
+
+    }
+
+    void attachWagonFromRight(int wagonId)
+    {
+        // Check if there is already a wagon on the train, if yes update the rightmost wagon
+        if(this->train_length == 0)
+        {
+            this->initialise_train(wagonId);
+        }
+        else
+        {
+            Wagon* old_right_wagon = this->right_wagon;
+            old_right_wagon->to_the_right = new Wagon(wagonId);
+            this->right_wagon = old_right_wagon->to_the_right;
+
+            // Update new rightmost wagon's properties
+            this->right_wagon->to_the_left = old_right_wagon;
+
+            this->train_length++;
+        }
+
+    }
+
+    int detachWagonFromLeft()
+    {
+        if(this->train_length == 0)
+        {
+            throw std::logic_error("Cannot remove wagon from train of length 0");
+        }
+        else
+        {
+            Wagon* removed_wagon = this->left_wagon;
+            this->left_wagon = removed_wagon->to_the_right;
+            int wagonID = removed_wagon->wagonID;
+
+            delete removed_wagon;
+            this->train_length--;
+
+            return wagonID;
+        }
+
+    }
+
+    int detachWagonFromRight()
+    {
+        if(this->train_length == 0)
+        {
+            throw std::logic_error("Cannot remove wagon from train of length 0");
+        }
+        else
+        {
+            Wagon* removed_wagon = this->right_wagon;
+            this->right_wagon = removed_wagon->to_the_left;
+            int wagonID = removed_wagon->wagonID;
+
+            delete removed_wagon;
+            this->train_length--;
+
+            return wagonID;
+        }
+
+    }
+
+    // void listWagons() // List from left to right
+    // {
+    //     Wagon* wagon = this->left_wagon;
+
+    //     while(wagon->to_the_right != NULL)
+    //     {
+    //         std::cout << wagon->wagonID << " ";
+
+    //         wagon = wagon->to_the_right;
+    //     }
+    // }
+};
+
+
+// Test execution time vs deque version
+#ifndef RunTests
+int main()
+{
+    TrainComposition train;
+
+    int no_wagons = 1000000;
+
+    auto start = std::chrono::high_resolution_clock::now();
+
+    for(int i = 1; i<no_wagons ; i++)
+    {
+        train.attachWagonFromLeft(i);
+    }
+
+    for(int i = no_wagons; i < no_wagons*2; i++)
+    {
+        train.attachWagonFromRight(i);
+    }
+
+    for(int i = 1; i<no_wagons ; i++)
+    {
+        //std::cout << train.detachWagonFromRight() << "\n";
+    }
+
+    for(int i = 0; i < no_wagons; i++)
+    {
+        //std::cout << train.detachWagonFromLeft() << "\n";
+    }
+
+    auto stop = std::chrono::high_resolution_clock::now();
+
+    auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(stop - start); 
+
+    // To get the value of duration use the count() 
+    // member function on the duration object 
+    std::cout << duration.count() << std::endl; 
+
+    // The original test case
+    train.attachWagonFromLeft(7);
+    train.attachWagonFromLeft(13);
+    train.attachWagonFromRight(15);
+    std::cout << train.detachWagonFromRight() << "\n"; // 15 
+    std::cout << train.detachWagonFromRight(); // 7
+}
+#endif