Question

I have been working on creating an RPG combat sim for code-practice. A single ‘battle’ constitutes a 3D vector based on number of rounds,number of fighter and number of Rolls (per fighter in each round) in that order. After hours of searching I have put together this code. I am aware there are easier ways to accomplish this (boost / matrix etc..) but I want to finish this and learn where my STL::vector manipulation is going wrong

#include <vector>
#include <algorithm>

using namespace std;

class Combat{
    private:
        int numberOfRounds;
        int numberOfCombatants;
        int numberOfRolls;
        int sidesDie;            
        vector <vector <vector <int> > > result;

    public:
        void printMenu();
        void battle();
        void printResult();
        int roll(int die);
};
int Combat::roll(int die)
{
    die=sidesDie;
    srand(time(0));
    int r=(1+rand()%die);
    return r;

void Combat::battle(){
    cout<<setw(10)<<" Computing results of battle ...\n";
    int i,j,k;
    for (i=0;i<numberOfRounds;++i){
        cout<<"Round number "<<i+1;
        for(j=0;j<numberOfCombatants;++j){
            for(k=0;k<numberOfRolls;++k){
                result[i][j].push_back(roll(sidesDie));

            }
            cout<<endl;
        }

        cout<<endl;

      }
}

The code above is supposed to create a 3D vector ‘result’ which should store dice-rolls inside cells per player per round. It crashes during execution without showing an error. i suspect the bug is in the way i am storing values inside the 3d vector

Answer 1

You are correct – your result variable is a vector of vector of vector of ints. In your battle loop, you are attempting to push_back into the innermost vector, but the outer two vectors don’t have any contents defined yet.

You’ll need to push_back an entry for i and j as well (of the appropriate subtype, e.g. vector < vector < int > >, and then vector < int >, to use the vector in this fashion.

edit

For instance:

int i,j,k;
vector<vector<int>> iType;
vector<int> jType;
for (i=0;i<numberOfRounds;++i)
{
    cout<<"Round number "<<i+1;
    result.push_back( iType );
    for(j=0;j<numberOfCombatants;++j)
    {
        result[i].push_back( jType );
        for(k=0;k<numberOfRolls;++k)
        {
            result[i][j].push_back(roll(sidesDie));

        }
        cout<<endl;
    }

    cout<<endl;

  }