Finding Shortest Distance on Graph -- Logic Issue - c++

Question

In my C++ course we have been working on graphs for a while, and there's a certain question that I've been stuck on for quite some time. The teacher gave us a program that created a graph of integers and then was able to find the shortest path between two integers in the graph. Our job was to adapt this to work for strings (specifically, find the shortest path only jumping to words that have 1 different letter than the previous word e.g bears -> beard).
Here is a sample of what I would expect my program to do:
Given the list [board, beard, bears, brand, boars, bland, blank]
it would create an edge matrix that resembled this:
board | beard boars
beard | board bears
bears | beard boars
brand | bland
boars | board bears
bland | brand blank
blank | bland
And then if asked to find the distance between board & bears it would output:
board->beard->bears
The way I adapted my program is that it creates a graph of a struct named 'node' which contains a number and a word. I use the number to compare the order within one vector to other variables, and the word to create the path. My adapted program successfully creates the graph from data in a text file and connects all words that have a 1 letter difference, however, when I run my function to find the shortest distance it bypasses my edges and simply print out that the start word and end word are a distance of 1 apart.
I will post my full, compile-able program below and explain what I know about the problem.
Here is a link to two pastebin links (I do not have a high enough reputation yet to post more than two links so I must combine them) The first is my full program, I have adapted it to use a set of words that I know are a word distance of 1 apart rather than a text file.
http://pastebin.com/W7HRZG2v
This second link is a download of the code my teacher gave (in case you wish to see a working version of the program)
I've narrowed the problem down to how I'm filling the vector "parents". Somehow it isn't generating properly and is creating an issue when the program tries to retrieve a path from it.
Here is a link to a photo (reputation not high enough to post images yet) comparing what the parents vector looks like in my teacher's "healthy" program (find distance between 2 & 5) to the parents vector in my program:
http://puu.sh/95zQI/26e9b83b9a.png
Notice how in my teacher's, 2 and 4, both integers used in the path, are present in the parents vector and called on to create it.
Notice how in mine the only word present in the parents vector is the beginning word, and hence it is the only word available to call on. However when comparing the way my teacher filled parents with the way I do, there are no differences I can see, aside from the fact that my parents is a string so I am entering a word instead of a number:
(my adapted version is on the left, teacher's is on the right)
if (distanceNodes[edgeNum] > distanceNodes[currNum] + 1) | if (distanceNodes[edge] > distanceNodes[curr] + 1)
{ | {
distanceNodes[edgeNum] = distanceNodes[currNum] + 1; | distanceNodes[edge] = distanceNodes[curr] + 1;
parents[edgeNum] = curr->word; | parents[edge] = curr;
} | }
If someone more proficient in graph application could look at this and assist me I would be extremely grateful. I've been stuck on this problem for over a week and the only tip my teacher will give me is that I should compare my program to his line by line; I did that and I still can't find the problem, I'm about ready to give up.
If you can help me, thank you very much,
Tristan

Answer 1

Here:
node * one = createNewNode(1, "board");
...
node * three = createNewNode(3, "bears");
...
insertEdge(&g, one, three);
The program correctly finds the edge you put there.
More generally, you must learn to step through your code and see what's happening.
And don't use global variables if you can help it.
EDIT:
I had some free time, so here's another problem:
int currNum = start->num;
while (! inTree[currNum])
{
...
parents[edgeNum] = curr->word;
...
}
You iterate by number, but you look things up by a pointer which you never update.
I'm sure there are other problems. The bottom line is that you're not checking things. For some reason, testing, which real coders do all the time, is never taught in programming courses.