C + +子集數組查找器循環與逗號結束？

Question

這裏是我的代碼

#include "iostream" 
using namespace std; 
void choice(); 
void Start(){ 
system("cls"); 
    char subset[100]; 
    int y,x; 
    cout << "Enter a Set"<<endl; 
    int pass = 0; 
    while (pass < 1){ 
     y = 0; 
     x = 0; 
     cin >> subset; 
      while(y < 100){ 
      if (subset[x+1] == '}') { cout<<"Invalid Set"<<endl<<"Enter a Set"<<endl; break; } 
      if (subset[x] == '}'&& subset[0] == '{') { cout << "Set Accepted"<<endl; pass = 1; break;} 
      x = x+2; 
      if (y == 99) {cout <<"Invalid Set"<<endl<<"Enter a Set"<<endl; } 
      y++; 
      } 
    }  
    int nofsubset = x/2; 
    int b = 1; 
    char arr[99]; 
    int n = nofsubset; 
     while(nofsubset!= 0) { 
      for(int l=0; l<n; l++){ 
      //cin >> arr[l]; 
      arr[l] = subset[b]; 
      b = b + 2; 
      } 
      for (int i=0; i<(1<<n); i++){ 
      cout << "{"; 
       for(int j=0; j<n; j++) {  
        if(i & (1 <<j)) { 
        cout << arr[j]; 
        }  
       } 
      cout <<"}"<<endl; 
      } 
      nofsubset = 0; 
     } 
    system("pause"); 
    choice(); 
} 

void choice(){ 
    system("cls"); 
    cout <<"**************************"<<endl; 
    cout <<"*      *"<<endl; 
    cout <<"* 1 - Generate Subsets *"<<endl; 
    cout <<"* 2 - Exit    *"<<endl; 
    cout <<"*      *"<<endl; 
    cout <<"**************************"<<endl; 
    int choice; 
    cin >> choice; 
    if(choice == 1){ Start();} 
    else{ return ;} 
} 

int main() { 
choice(); 
} 

這段代碼將使找到一套子集，例如我進入{1,2,3}，它會產生

{} 
{1} 
{2} 
{12} 
{3} 
{13} 
{23} 
{123} 

我的教授想要的是出來把它放在格式逗號這樣

{} 
{1} 
{2} 
{1,2} 
{3} 
{1,3} 
{2,3} 
{1,2,3} 

任何人都可以請幫我修改我的代碼，我不能似乎只是把「」循環陣列上，因爲ITL農產品{1,2,3，}

在此先感謝！

Answer 1

 cout << "{"; 
      bool first = true; 
      for(int j=0; j<n; j++) {  
       if(i & (1 <<j)) { 

       if (!first) cout << ","; // <<< try this 
       first = false; 

       cout << arr[j]; 
       }  
      } 
     cout <<"}"<<endl;