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ex.4.44.cpp
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ex.4.44.cpp
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// ex.4.44
// en: Provide an implementation for your deque interface (Exercise
// 4.43) that uses an array for the underlying data structure.
// ru: Напишите реализацию для интерфейса дека (упр. 4.43), в которой
// в качестве базовой структуры данных используется массив.
#include <memory>
#include <stdexcept>
#include <catch.hpp>
template <typename T>
class Deque {
public:
explicit Deque(int capacity)
: n_(capacity + 1), q_(new T[n_]), head_(n_), tail_(0) {}
~Deque() { delete[] q_; }
bool Empty() const { return head_ % n_ == tail_; }
bool Full() const { return tail_ + 1 == head_; }
void PushFront(T v) {
if (Full()) Error("deque is full");
--head_;
if (head_ < 0) head_ = n_ - 1;
q_[head_] = v;
}
void PushBack(T v) {
if (Full()) Error("deque is full");
q_[tail_++] = v;
tail_ %= n_;
}
T PopFront() {
if (Empty()) Error("deque is empty");
head_ %= n_;
return q_[head_++];
}
T PopBack() {
if (Empty()) Error("deque is empty");
--tail_;
if (tail_ < 0) tail_ = n_ - 1;
return q_[tail_];
}
private:
void Error(const char* msg) const { throw std::length_error(msg); }
private:
int n_;
T* q_;
int head_;
int tail_;
};
TEST_CASE("deque") {
Deque<int> d{3};
REQUIRE(d.Empty());
REQUIRE_THROWS_AS(d.PopFront(), std::length_error);
REQUIRE_THROWS_AS(d.PopBack(), std::length_error);
SECTION("use as stack (front)") {
d.PushFront(1);
d.PushFront(2);
d.PushFront(3);
REQUIRE_THROWS_AS(d.PushBack(4), std::length_error);
REQUIRE_THROWS_AS(d.PushFront(4), std::length_error);
REQUIRE(d.PopFront() == 3);
REQUIRE(d.PopFront() == 2);
REQUIRE(d.PopFront() == 1);
}
SECTION("use as stack (back)") {
d.PushBack(1);
d.PushBack(2);
d.PushBack(3);
REQUIRE_THROWS_AS(d.PushBack(4), std::length_error);
REQUIRE_THROWS_AS(d.PushFront(4), std::length_error);
REQUIRE(d.PopBack() == 3);
REQUIRE(d.PopBack() == 2);
REQUIRE(d.PopBack() == 1);
}
SECTION("use as queue (back -> front)") {
d.PushBack(1);
d.PushBack(2);
d.PushBack(3);
REQUIRE_THROWS_AS(d.PushBack(4), std::length_error);
REQUIRE_THROWS_AS(d.PushFront(4), std::length_error);
REQUIRE(d.PopFront() == 1);
REQUIRE(d.PopFront() == 2);
REQUIRE(d.PopFront() == 3);
}
SECTION("use as queue (front -> back)") {
d.PushFront(1);
d.PushFront(2);
d.PushFront(3);
REQUIRE_THROWS_AS(d.PushBack(4), std::length_error);
REQUIRE_THROWS_AS(d.PushFront(4), std::length_error);
REQUIRE(d.PopBack() == 1);
REQUIRE(d.PopBack() == 2);
REQUIRE(d.PopBack() == 3);
}
SECTION("use as deque (mixed)") {
d.PushBack(1);
d.PushFront(2);
d.PushBack(3);
REQUIRE_THROWS_AS(d.PushBack(4), std::length_error);
REQUIRE_THROWS_AS(d.PushFront(4), std::length_error);
REQUIRE(d.PopFront() == 2);
REQUIRE(d.PopBack() == 3);
REQUIRE(d.PopFront() == 1);
}
REQUIRE(d.Empty());
REQUIRE_THROWS_AS(d.PopFront(), std::length_error);
REQUIRE_THROWS_AS(d.PopBack(), std::length_error);
}