localstatic.cpp

来自「包含C++中map」· C++ 代码 · 共 46 行

#include<vector>
#include<iostream>

using namespace std;

inline bool check_validity(int pos)
{
	return (pos <= 0 || pos > 64) ? false : true;
}

const vector<int>*
pentagonal_series(int pos)
{
	static vector<int> _elems;
	if(check_validity(pos) && (pos > _elems.size()))
		for(int ix=_elems.size()+1;ix <=pos;++ix)
			_elems.push_back((ix*(3*ix-1))/2);
	return &_elems;
}

bool pentagonal_elem(int pos,int &elem)
{
	if(!check_validity(pos))
	{
		cout << "Sorry. Invalid position: " << pos << endl;
		elem=0;
		return false;
	}
	const vector<int> *pent=pentagonal_series(pos);
	elem=(*pent)[pos-1];
	return true;
}

int main()
{
	int elem;
	if(pentagonal_elem(8,elem))
		cout << "element 8 is " << elem << '\n';
	if(pentagonal_elem(88,elem))
		cout << "element 88 is " << elem << '\n';
	if(pentagonal_elem(12,elem))
		cout << "element 12 is " << elem << '\n';
	if(pentagonal_elem(64,elem))
		cout << "element 64 is " << elem << '\n';
	return 1;
}