枚举

排列

全排列

void AllPermutation(int l, int r)
{
	vector<int>p;
	for (int i = l; i <= r; ++i)
	{
		p.push_back(i);
	}
	do
	{
		//do something
	} while (next_permutation(p.begin(), p.end()));
}

子集

枚举全部子集

void AllSubset(int s)
{
	for (int i = s; i; i = (i - 1) & s)
	{
		//do something
	}
}

枚举k大小子集

void GospersHack(int k, int n)
{
	int cur = (1 << k) - 1, limit = (1 << n);
	while (cur < limit)
	{
		// do something
		int lb = cur & -cur, r = cur + lb;
		cur = (((r ^ cur) >> 2) / lb) | r;
	}
}