How to perform a recursive search?

Question

I have a Task class which can have sub tasks of the same type

public class Task
{
  public DateTime Start { get; set;}
  public DateTime Finish { get; set;}
         


        

Answer 1

Svick's solution is fine, but I thought I'd add a bit more general advice. It seems like you are new to writing recursive methods and were struggling a bit there. The easiest way to write a recursive method is to strictly follow a pattern:

Result M(Problem prob)
{
    if ()
        return ;
    // The problem cannot be solved easily.
    Problem smaller1 = 
    Result result1 = M(smaller1);
    Problem smaller2 = 
    Result result2 = M(smaller2);
    ...
    Result finalResult = 
    return finalResult;
}

So suppose you want to solve the problem "what is the maximum depth of my binary tree?"

int Depth(Tree tree)
{
    // Start with the trivial case. Is the tree empty?
    if (tree.IsEmpty) return 0;
    // The tree is not empty. 
    // Reduce the problem to two smaller problems and solve them:
    int depthLeft = Depth(tree.Left);
    int depthRight = Depth(tree.Right);
    // Now combine the two solutions to solve the larger problem.
    return Math.Max(depthLeft, depthRight) + 1;
}

You need three things to make recursion work:

• The problem has to get smaller every time you recurse.
• The problem has to eventually get so small that it can be solved without recursion
• The problem has to be solvable by breaking it down into a series of smaller problems, solving each one, and combining the results.

If you cannot guarantee those three things then do not use a recursive solution.