C++ recursion segfault. Can you help me see what I'm doing wrong?

Question

This is the first time I've used recursion to do something other than find the factorial of a number. I'm building a program to find words in a boggle board. Following is the function that is resulting in segfaults:

void findWord(vector<string>& board, set<string>& dictionary,
          string prefix, int row, int column){
  prefix += getTile(board, row, column);
  if(prefix.length() > biggestWordLength)
    return;
  if(isOutOfBounds(row, column))
    return;
  if(isWord(prefix, dictionary) == 1)
    foundWords.insert(prefix);
  if(isWord(prefix, dictionary) == 0)
    return;
  //Note: this does not prevent using the same tile twice in a word
  findWord(board, dictionary, prefix, row-1, column-1);
  findWord(board, dictionary, prefix, row-1, column);
  findWord(board, dictionary, prefix, row-1, column+1);
  findWord(board, dictionary, prefix, row, column-1);
  findWord(board, dictionary, prefix, row, column+1);
  findWord(board, dictionary, prefix, row+1, column-1);
  findWord(board, dictionary, prefix, row+1, column);
  findWord(board, dictionary, prefix, row+1, column+1);
}

Answer 1

You are recursing in all directions in all cases. Consider this reduced recursion version:

void findword(... int x, int y, ...) {
   ...
   findword(... x, y+1, ...);
   findword(... x, y-1, ...);
   ...
}

Now consider when it is called for x == 5 and y == 5 (for example, any other position would be just as good). I am using indentation below to represent nested calls:

findword(... 5, 5, ...)
   findword(..., 5, 6, ...)    // x, y+1
      ...
   findword(..., 5, 5, ...)    // x, y-1
      // ouch! this is just the same as before, so it will eventually:
      findword(..., 5, 6, ...)
      findword(..., 5, 5, ...)
          // ouch!... here again! shall I continue?

Now, think about the algorithm. When looking for a word, you first select the first character, then a direction and then test going in that direction how many letters can make up a word. The algorithm you implemented attempts to find words not just in lines but in any random shape.