groupdefenderscommentsanditerators.cpp

   /*
     Print out all ways for attackers to be blocked. blockAssignments maps ids of attackers to 
     vectors of defender ids for which blocks have already been chosen. defenders/defendersIterator specify
     defenders that could block any of the attackers. This method iterates over all ways to choose blocks for 
     the remaining defenders.

     example input: groupDefenders({0:[2 3] 1:[4 5]}, [6 7 8 9], 3)
      
     output:

      0: 2 3
      1: 4 5
      
      0: 2 3 9
      1: 4 5
      
      0: 2 3
      1: 4 5 9
   */
   void groupDefenders(map<int, vector<int>> blockAssignments, const vector<int>& defenders, vector<int>::iterator defendersIterator) {
      int x = 0;
      for (auto const& x : blockAssignments) {
         cout << x.first << ": ";
         for (int defender:x.second) {
            cout << defender << " ";
         }
         cout << "\n";
      }

      if(defendersIterator == defenders.end()) {
         return;
      }
      
      // choose all the possible ways that defenders[indexOfDefender] can be allocated, and print out each of them.
      for (auto& attacker : blockAssignments) {
         // push a defender into blockAssignments
         attacker.second.push_back(*defendersIterator);
         // recurse to print it and continue to push more defenders recursively
         groupDefenders(blockAssignments, defenders, ++defendersIterator);
         // pop the defender so it can be pushed to the next possible attacker in blockAssignments when looping
         attacker.second.pop_back();
      }
   }