排列、组合、枚举子集

#include <cstdio>
#include <cstring>
#include <vector>
using namespace std;

void DoSth(vector<int>& chosen)
{
	for(int i=0; i<chosen.size(); i++)
		printf("%d ", chosen[i]);
	printf("\n");
}

void Combination1(int n, int m, int begin, vector<int>& chosen)
{
	if(n - begin + 1 < m)
		return;
	chosen.push_back(begin);
	if(m - 1 == 0)
		DoSth(chosen)
	else
		Combination1(n, m - 1, begin + 1, chosen);
	chosen.pop_back();
	Combination1(n, m, begin + 1, chosen);
}

void Combination2(int n, int m, int begin, vector<int>& chosen)
{
	if(n - begin + 1 < m)
		return;
	if(m == 0)
	{
		DoSth(chosen);
		return;
	}
	for(int i=begin; i<=n; i++)
	{
		chosen.push_back(i);
		Combination2(n, m - 1, i + 1, chosen);
		chosen.pop_back();
	}
}

void Combination(int n, int m)
{
	vector<int> chosen;
	Combination1(n,m,1,chosen);
}

void Permutation(int n, int m, int k, vector<int> &chosen)
{
	if(chosen.size()>m || chosen.size()+n-k+1<m)
		return;
	if(k==m)
	{
		for(int i=0; i<chosen.size(); i++)
			printf("%d ",chosen[i]+1);
		printf("\n");
		return;
	}
	for(int i=0; i<n; i++)
	{
		int ok=true;
		for(int j=0; j<chosen.size(); j++)
		{
			if(i==chosen[j])
			{
				ok=false;
				break;
			}
		}
		if(ok)
		{
			chosen.push_back(i);
			Permutation(n,m,k+1,chosen);
			chosen.pop_back();
		}
	}
}

void Permutation(int n, int m)
{
	vector<int> chosen;
	Permutation(n, m, 0, chosen);
}

void Subset(int n, int begin, vector<int> &chosen)
{
	for(int i=0; i<chosen.size(); i++)
		printf("%d ", chosen[i]+1);
	printf("\n");
	if(begin==n)
		return;
	for(int i=begin; i<n; i++)
	{
		chosen.push_back(i);
		Subset(n, i+1, chosen);
		chosen.pop_back();
	}
}

void Subset(int n)
{
	vector<int> chosen;
	Subset(n, 0, chosen);
}

int main()
{
	int op;
	do{
		printf("Combination(1) or Permutation(2) or Subset(3)?\n");
		int n, m;
		scanf("%d",&op);
		printf("Input n and m\n");
		if(op==3)
			printf("Just input m to your heart's content.\n");
		scanf("%d%d",&n,&m);
		switch(op)
		{
		case 1:
			Combination(n,m);
			break;
		case 2:
			Permutation(n, m);
			break;
		case 3:
			Subset(n);
			break;
		}
		printf("continue(1) or exit(0)?\n");
		scanf("%d",&op);
	}while(op==1);
	return 0;
}