Moved implementations to folder

1 files changed, 134 insertions, 0 deletions

diff --git a/impls/list.cpp b/impls/list.cpp
new file mode 100644
index 0000000..b87a3e2
--- /dev/null
+++ b/impls/list.cpp
@@ -0,0 +1,134 @@
+/* list.cpp
+ * Date: 2021-11-20
+ * Author: Aryadev Chavali
+ */
+
+#include <cstdio>
+#include <cstdlib>
+#include <iostream>
+
+template <typename T>
+struct List
+{
+  T value;
+  List<T> *next;
+
+  List(T val, List<T> *n)
+  {
+    value = val;
+    next  = n;
+  }
+
+  ~List()
+  {
+    if (next == nullptr)
+      return;
+    delete next;
+  }
+};
+
+template <typename T>
+List<T> *append(List<T> *lst, T value)
+{
+  List<T> *node;
+  if (lst == nullptr)
+    return new List<T>(value, nullptr);
+
+  for (node = lst; node->next != nullptr; node = node->next)
+    continue;
+
+  node->next = new List<T>(value, nullptr);
+  return lst;
+}
+
+/** Reverse a list
+ */
+template <typename T>
+List<T> *reverse(List<T> *lst, List<T> *prev = nullptr)
+{
+  auto next = lst->next;
+  lst->next = prev;
+  if (next == nullptr)
+    return lst;
+  return reverse(next, lst);
+}
+
+template <typename T, typename U>
+List<U> *map(List<T> *lst, U (*f)(T))
+{
+  if (!lst)
+    return nullptr;
+  return new List<U>(f(lst->value), map(lst->next, f));
+}
+
+template <typename T>
+T reduce(List<T> *lst, T (*reducer)(T, T), T init = 0)
+{
+  if (!lst)
+    return init;
+  else if (!init)
+    init = lst->value;
+  else
+    init = reducer(init, lst->value);
+  return reduce(lst->next, reducer, init);
+}
+
+template <typename T>
+List<T> *filter(List<T> *lst, bool (*f)(T), List<T> *new_lst = nullptr)
+{
+  if (!lst)
+    return new_lst;
+  if (f(lst->value))
+    new_lst = append(new_lst, lst->value);
+  return filter(lst->next, f, new_lst);
+}
+
+template <typename T>
+std::ostream &operator<<(std::ostream &ostream, const List<T> *lst)
+{
+  if (!lst)
+    return ostream;
+  ostream << "|" << lst->value << lst->next;
+  return ostream;
+}
+
+int main(void)
+{
+  puts("Create linked list with 1..10");
+  auto lst = append<int>(nullptr, 1);
+  for (int i = 2; i <= 10; ++i)
+    lst = append(lst, i);
+  printf("Current output for list: ");
+  std::cout << lst << std::endl;
+  lst = reverse(lst);
+  printf("Reverse list: ");
+  std::cout << lst << std::endl;
+  puts("Reverse list again...");
+  printf("Map list with f(x) = 2x: ");
+  auto mapped = map<int, int>(lst = reverse(lst),
+                              [](int x)
+                              {
+                                return x * 2;
+                              });
+  std::cout << mapped << std::endl;
+  delete mapped;
+  printf("Sum all numbers in list: ");
+  std::cout << reduce<int>(
+    lst,
+    [](int a, int b)
+    {
+      return a + b;
+    },
+                   0)
+            << std::endl;
+  printf("Print all even numbers 1..10: ");
+  auto evens = filter<int>(lst,
+                           [](int a)
+                           {
+                             return a % 2 == 0;
+                           });
+  std::cout << evens << std::endl;
+  delete lst;
+  delete evens;
+  return 0;
+}