不同元素的排列与组合

#include<iostream>

#include<vector>

#include<string>

#include<algorithm>

#include<numeric>

using namespace std;

vector<vector<int> > ret;

vector<int> sub;

int num = 0;
void helper(int* str, int n,int i) ///递归求组合

{

  if(i == n)

  {

    ret.push_back(sub);

    return;

  }

  helper(str, n,i+1);

  sub.push_back(str[i]);

  helper(str, n,i+1);

  sub.pop_back(); ///看来这个要恢复场景~

}
void helper2(int* str, int n,int i)

{

  if(i == n - 1)

  {

      num++;

      cout<<num<<endl;

      return ;

  }
for(int j = i;j < n;j++)

  {

    swap(str[i],str[j]);

    helper2(str, n,i + 1);

    swap(str[i],str[j]);

  }
}
int main()

{

    ret.clear();

    sub.clear();

    int str[] = {1,2,3,4,5};

    helper2(str, 5, 0);

    //for(int i = 0;i< ret.size();i++)

    //{

    //    for(int j = 0;j< ret[i].size();j++)

    //        cout<<ret[i][j]<<" ";

    //        cout<<endl;

    //}

}

不同元素的排列与组合