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/* 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;
}
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