Question

I am doing my project on Missionaries and Cannibals using C#. I have used two search algorithms namely breadth first search and depth first search. Using Breadth first search, the program finds the result at level 12 from the root. But using Depth first search, it can not find solution and this hangs my computer. I think it enters a cycle in the graph. So my question is, can’t i use Depth first search to solve Missionaries and cannibals problem?

Code for Breadth first search is

public State getSolutionStatesBFS(State StartState, State EndState) 
        {
            State CurState = new State();
            ArrayList visited = new ArrayList();
            addStateToAgenda(StartState, true);
            while (searchAgenda.Count > 0) {
                CurState = (State)searchAgenda.Dequeue();

              if (CurState.Equals(EndState)) {
                    break;
              } else {
                  if (!isVisited(CurState, visited))
                  {
                      generateSucessors(CurState, true);
                      visited.Add(CurState);
                  }
              }

            }
            return CurState;
        } 

and the code for depth first search is

public State getSolutionStatesDFS(State StartState, State EndState)
        {
            State CurState = new State();
            ArrayList visited = new ArrayList();
            addStateToAgenda(StartState, false);
            while (searchAgendaS.Count > 0)
            {
                CurState = (State)searchAgendaS.Pop();

                if (CurState.Equals(EndState))
                {
                    break;
                }
                else
                {
                    if(!isVisited(CurState,visited))
                    {
                        generateSucessors(CurState, false);
                    }
                }
            }
            return CurState;
        }

Answer 1

It is hard to tell answer seeing your code. However, based upon my experience: a DFS search does not provide complete solution. There is a good possibility that your code might have got stuck into some infinite loop (which is common with dfs) or (since, you are checking isVisited), there is a possibility that you are not reaching the end goal.