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/* list.cpp
* Date: 2021-11-20
* Author: Aryadev Chavali
*/
#include <cstdio>
#include <iostream>
#include <cstdlib>
template <typename T>
struct List
{
T value;
struct List<T> *next;
~List()
{
if (next == nullptr)
return;
delete next;
}
};
template <typename T>
List<T> *append(List<T> *lst, T value)
{
List<T> *node;
if (lst == nullptr)
{
node = new List<T>;
node->value = value;
node->next = nullptr;
return node;
}
for (node = lst; node->next != nullptr; node = node->next)
continue;
node->next = new List<T>;
node->next->value = value;
node->next->next = 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>
void map(List<T> *lst, U (*f)(T))
{
if (!lst)
return;
lst->value = 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;
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: ");
map<int, int>(lst = reverse(lst), [](int x){ return x * 2; });
std::cout << lst << std::endl;
puts("Reverse map...");
map<int, int>(lst, [](int x){ return x / 2; });
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;
}
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