Originally Posted by
DaDaDan
As I noted above, the problem is that extending a route can lower its price.
And delta doesn't need to fly 1000000000 routes a day to cause this issue. Even with Delta's current route structure, and limiting yourself just to DL-marketed flights, there are already sufficiently many ways to get from A to B that you cannot practically check them all.
No DaDaDan extending broken fare routes can
not lower the price. This problem requires solving the "what is the lowest AAA-ZZZ fare available" and then looking for combinations of fares that get you from AAA to BBB without going over that price.
So:
(1) Lowest available "married segment" fare to destination
(2) Find fares (married or individual flight) from origin airport that are lower than fare found in (1)
(3) Find fares (married or individual flight) from connecting airport found in (2) which combine to be less than the currently best fare or combination of fares
(4) For each fare or combinations of fares found in (3) iterate (3) until at destination
The reality is that you could stop at a couple connections for practical purposes...