From 497ab41504532e5a77e6511742604ad8249eb549 Mon Sep 17 00:00:00 2001
From: sikoeh <111141745+sikoeh@users.noreply.github.com>
Date: Tue, 16 Aug 2022 12:37:54 +0200
Subject: [PATCH] added implementation of a single linked list

---
 .../single_linked_list/single_linked_list.cpp | 118 ++++++++++++
 .../single_linked_list/single_linked_list.hpp | 172 ++++++++++++++++++
 2 files changed, 290 insertions(+)
 create mode 100644 data_structures/single_linked_list/single_linked_list.cpp
 create mode 100644 data_structures/single_linked_list/single_linked_list.hpp

diff --git a/data_structures/single_linked_list/single_linked_list.cpp b/data_structures/single_linked_list/single_linked_list.cpp
new file mode 100644
index 0000000..cefc5f2
--- /dev/null
+++ b/data_structures/single_linked_list/single_linked_list.cpp
@@ -0,0 +1,118 @@
+/*
+*   Author: sikoeh (https://github.com/sikoeh)
+*   
+*   Example usage of the single linked list.
+*   This file aims to test the size of the list and position of it's elements after the different operations.
+*   Zero memory leaks according to valgrind.
+*   Compiled and executed with following commands:
+*   > g++ single_linked_list.hpp
+*   > g++ single_linked_list.cpp
+*   > ./a.out
+*/
+
+#include "single_linked_list.hpp"
+
+#include <cassert>
+
+//dummy that is used as list data for later tests
+class dummy{
+ public:
+    dummy(int x, int y)
+        :
+        x_(x),
+        y_(y)
+    {};
+
+    //simple compare of x and y values
+    bool operator ==(const dummy& other){
+        bool res = x_ == other.x_;
+        res &= y_ == other.y_;
+        return res;
+    }
+
+ private:
+    int x_;
+    int y_;
+};
+
+
+
+int main(){
+    //Tests with simple integer
+    single_linked_list<int> list;
+
+    list.insert(1);
+    list.insert(2);
+    list.insert(3);
+    list.insert(4);
+    list.insert(5);
+
+    assert(list.size() == 5);
+    assert(list.at(3) == 4);
+    
+    list.remove(4);
+
+    assert(list.size() == 4);
+    assert(list.at(3) == 5);
+
+
+
+    //Check for correct size after invalid position input
+    try{
+        list.remove_at(200);
+        assert(false);
+    }
+    catch(const std::exception& e){
+        assert(list.size() == 4);
+    }
+
+    list.insert_at(0, 0);
+    assert(list.size() == 5);
+    assert(list.at(0) == 0);
+
+    list.remove_at(0);
+    assert(list.size() == 4);
+    assert(list.at(0) == 1);
+
+    list.insert_at(7, 3);
+    assert(list.size() == 5);
+    assert(list.at(3) == 7);
+
+    list.remove_at(3);
+    assert(list.size() == 4);
+    assert(list.at(3) == 5);
+
+    //Test copy constructor
+    single_linked_list<int> copy(list);
+
+    assert(copy.size() == 4);
+    assert(copy.at(3) == 5);
+
+    //Test move constructor
+    single_linked_list<int> move_list(std::move(copy));
+    assert(move_list.size() == 4);
+    assert(move_list.at(3) == 5);
+
+    //Tests with dummy class
+    single_linked_list<dummy&> list2;
+
+    dummy d1(1, 2);
+    dummy d2(2, 3);
+    dummy d3(3, 4);
+    dummy d4(5, 6);
+
+    list2.insert(d1);
+    list2.insert(d2);
+    list2.insert(d3);
+    list2.insert(d4);
+
+    assert(list2.size() == 4);
+    assert(list2.at(0) == d1);
+
+    list2.remove(d2);
+
+    assert(list2.size() == 3);
+    assert(list2.at(1) == d3);
+
+    return EXIT_SUCCESS;
+}
\ No newline at end of file
diff --git a/data_structures/single_linked_list/single_linked_list.hpp b/data_structures/single_linked_list/single_linked_list.hpp
new file mode 100644
index 0000000..e12ab16
--- /dev/null
+++ b/data_structures/single_linked_list/single_linked_list.hpp
@@ -0,0 +1,172 @@
+/*
+*   Author: sikoeh (https://github.com/sikoeh)
+*   
+*   Implementation of a simple single linked list with the help of templates.
+*   Objects stored in this list must have a copy-constructor and a valid == operator.
+*/
+#ifndef INCLUDED_SINGLE_LINKED_LIST
+#define INCLUDED_SINGLE_LINKED_LIST
+
+#include <stdexcept>
+
+template<class T>
+class single_linked_list{
+ public:
+
+    single_linked_list()
+        :
+        head_(nullptr),
+        size_(0)
+    {};
+
+    single_linked_list(const single_linked_list<T>& other)
+        :
+        head_(nullptr),
+        size_(0)
+    {
+        list_element* iterator = other.head_;
+        while(iterator != nullptr){
+            insert(iterator->data_);
+            iterator = iterator->next_;
+        }
+    };
+
+    single_linked_list(single_linked_list<T>&& other)
+        :
+        head_(other.head_),
+        size_(other.size_)
+    {
+        other.head_ = nullptr;
+        other.size_ = 0;
+    };
+
+
+    ~single_linked_list(){
+        list_element* to_delete = head_;
+        while(to_delete != nullptr){
+            head_ = to_delete->next_;
+            delete to_delete;
+            to_delete = head_;
+        }
+    };
+
+    //insert at the end
+    void insert(const T& element){
+        list_element* new_element = new list_element(nullptr, element);
+
+        if(head_ == nullptr){
+            head_ = new_element;
+            ++size_;
+            return;
+        }
+
+        list_element* iterator = head_;
+        while(iterator->next_ != nullptr)
+            iterator = iterator->next_;
+
+        iterator->next_ = new_element;
+        ++size_;
+    };
+
+    //insert at the given position (0 is head)
+    void insert_at(const T& element, int position){
+        if(position > size_ || position < 0){
+            throw std::runtime_error("Invalid position");
+        }
+
+        if(position == 0){
+            list_element* new_element = new list_element(head_, element);
+            head_ = new_element;
+            ++size_;
+            return;
+        }
+
+        list_element* iterator = head_;
+        for (int i = 0; i < position-1; ++i)
+        {
+            iterator = iterator->next_;
+        }
+        
+        list_element* new_element = new list_element(iterator->next_, element);
+        iterator->next_ = new_element;
+        ++size_;
+    };
+
+    //remove the first element that is equal to the parameter (checked by == operator)
+    //does nothing in case there is no such element
+    void remove(const T& element){
+        list_element* iterator = head_;
+        if(element == head_->data_){
+            head_ = head_->next_;
+            delete iterator;
+            return;
+        }
+
+        while (iterator != nullptr)
+        {
+            list_element* next_element = iterator->next_;
+            if(next_element->data_ == element){
+                iterator->next_ = next_element->next_;
+                delete next_element;
+                --size_;
+                return;
+            }
+            iterator = iterator->next_;
+        }
+    };
+
+    //remove element at given position (0 is head)
+    void remove_at(int position){
+        if(position < 0 || position >= size_)
+            throw std::runtime_error("Invalid position");
+
+        if(position == 0){
+            list_element* new_head = head_->next_;
+            delete head_;
+            head_ = new_head;
+            --size_;
+            return;
+        }
+
+        list_element* iterator = head_;
+        for(int i = 0; i < position - 1; ++i)
+            iterator = iterator->next_;
+        
+        list_element* to_delete = iterator->next_;
+        iterator->next_ = to_delete->next_;
+        delete to_delete;
+        --size_;
+    };
+
+    //return a reference to the element at the given position (0 is head)
+    T& at(int position) const{
+        if(position < 0 || position >= size_)
+            throw std::runtime_error("Invalid position");
+
+        list_element* iterator = head_;
+        for(int i = 0; i < position; ++i){
+            iterator = iterator->next_;
+        }
+        return iterator->data_;
+    };
+
+    int size() const{
+        return size_;
+    };
+
+ private:
+    struct list_element{
+        list_element(list_element* next, T data)
+            :
+            next_(next),
+            data_(data)
+        {};
+        list_element* next_;
+        T data_;
+    };
+
+    list_element* head_;
+    int size_;
+};
+
+#endif
\ No newline at end of file