day9.cpp

#include <iostream>

const int ArrSize = 44;

struct ArrNode{
	int size;
	ArrNode* prev;
	ArrNode* next;
	int arr[ArrSize] = { 0 };

	ArrNode() : size( 0 ), prev( nullptr ), next( nullptr ) {}
	ArrNode( ArrNode* p, ArrNode* n ) : size( 0 ), prev( p ), next( n ) 
	{
		p->next= this;
		n->prev= this;
	};
};


struct ArrNode_insertPos {
	ArrNode* node;
	int index;
};



ArrNode_insertPos insert( ArrNode* node, int index, int elem );
ArrNode_insertPos remove( ArrNode* node, int index, int* out_elem );


ArrNode_insertPos append_wrap_2( ArrNode_insertPos pos, int elem )
{
	return insert( pos.node, pos.index + 2, elem );
}


ArrNode_insertPos remove_wrap_7( ArrNode_insertPos pos, int* out_elem )
{
	return remove( pos.node, pos.index - 7, out_elem );
}

void day_09( ArrNode* root1, int max_elem, int max_players )
{
	ArrNode* current = root1;
	insert( current, 0, 0 );

	ArrNode_insertPos pos = ArrNode_insertPos{ root1, 0 };
	int player = 1;
	int64_t* score = new int64_t[max_players]();

	for( int elem=1; elem <= max_elem; ++elem ) {
		if( elem % 23 == 0 ) {
			int out_elem;
			pos = remove_wrap_7( pos, &out_elem );
			score[player] += (int64_t) (elem + out_elem);
		}
		else {
			pos= append_wrap_2( pos, elem );
		}
		player = (player+1)%max_players;
	}

	int64_t max = 0;
	for( int i=0; i < max_players; ++i ) {
		if( score[i] > max ) max= score[i];
	}
}

int main()
{
	ArrNode* root1 = new ArrNode();
	ArrNode* root2 = new ArrNode( root1, root1 );

	const int N = 1;
	const int players = 1;
	day_09( root1, N, players );
}