标签：c++   leetcode   算法   

题目：

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

第二个思想是递归，这个元素放或者不放

#include <iostream>
#include <vector>
#include <string>
#include <algorithm> 

using namespace std;


void helper(vector<int>& vec,int begin,int& num,vector<int>& subset)
{
	if(begin >= vec.size() || num<0 )
		return ;
	subset.push_back(vec[begin]);
	num--;
	if(num == 0)
	{
		int i;
		for(i=0;i<subset.size();i++)
			cout<<subset[i]<<" ";
		cout<<endl;
	}
	helper(vec,begin+1,num,subset);
	subset.pop_back();
	num++;
	helper(vec,begin+1,num,subset); 
}

void Combination(vector<int>& vec,int k)
{
	if(vec.size()==0 || k <0)
		return ;
	vector<int> subset;
	sort(vec.begin(),vec.end());
	helper(vec,0,k,subset);
}

void Subsets(vector<int>& vec)
{
	int i;
	for(i=0;i<=vec.size();i++)
		Combination(vec,i);
}



void generate(vector<int> res, vector<int> &S, int i)  
    {  
        if(i == S.size())  
        {  
			for(int j=0;j<res.size();j++)
				cout<<res[j]<<" ";
			cout<<endl;
            //return;  
        }  
        else  
        {  
            generate(res, S, i+1);  
            res.push_back(S[i]);  
            generate(res, S, i+1);  
        }  
    }  

void SubsetSecond(vector<int>& vec)
{
	if(vec.size()<=0)
		return;
	
	sort(vec.begin(),vec.end());
	vector<int> result;
	generate(result,vec,0);
	 
}

int main() 
{
	int array[]={1,2,3};
	vector<int> vec(array,array+sizeof(array)/sizeof(int));
	SubsetSecond(vec);
	return 0;
}

Subsets--LeetCode

标签：c++   leetcode   算法   

原文地址：http://blog.csdn.net/yusiguyuan/article/details/44856059