PS/CP를 위한 원형 큐 클래스. Range-based for를 통해 BFS를 할 수 있습니다. std::queue와 같은 함수 기능을 제공합니다. || Circular buffer class for Problem Solving/Competitive programming. Can be used with a range-based for statement in BFS. Provides the same functionality with std::queue.

circular_buffer.cpp

#include<exception>
using namespace std;

//////// BEGIN STRUCT DEFINITION ////////
template<class T, size_t sz>
struct circular_buffer
{
	struct It
	{
		circular_buffer<T,sz>&par;
		size_t abspos;
		bool is_end;
		It&& operator++(int)
		{It pre=*this;abspos++;par.pop();return pre;}
		It& operator++()
		{abspos++;par.pop();return *this;}
		T& operator*()
		{return par.data[abspos%sz];}
		bool operator==(It r)
		{
			if(&r.par!=&par)return false;
			else if(is_end) return r.abspos==par.ed;
			else if(r.is_end) return abspos==par.ed;
			else return r.abspos==abspos;
		}
	};
	using iterator=It;
	using const_iterator=const It;
	T data[sz];
	size_t bg,ed;
	circular_buffer():bg(0),ed(0){}
	T& front()
	{return data[bg%sz];}
	void push(T&& val)
	{
		if(ed==bg+sz)throw out_of_range("Circular Buffer Full"s);
		else data[ed++]=val;
	}
	void pop()
	{
		if(ed==bg)throw out_of_range("Circular Buffer Empty"s);
		else bg++;
	}
	It begin()
	{return It{*this,bg,false};}
	It end()
	{return It{*this,ed,true};}
	size_t size()
	{return ed-bg;}
	bool empty()
	{return bg==ed;}
	void swap(circular_buffer<T,sz>&other)
	{
		swap(data,other.data);
	}
};
//////// END STRUCT DEFINITION ////////