I solved this problem using logic,
Walk = A -> C walking time * P
Train = A -> C walking time* P (+) waiting time to board train (+) train travel time * Q (+) D -> B walking time * P
But the logic kept failing
After seeing someone else accepted solution, they just did
Train = Y (+) train travel time * Q (+) D -> B walking time * P
Can anyone help here?
@ssjgz for the rescue
Did he teleport from A -> C to board train, smh 
CodeChef: Practical coding for everyone 
Assume the journey starts at time 0.
If the time taken to get to the train station exceeds Y, then he misses the train.
Otherwise, he has to wait for the train to arrive, which happens at time Y.
So in my solution, max(trainLeaveTime, timeWalkToTrain) will always equal trainLeaveTime (= Y), I think, so I should probably just replace it with trainLeaveTime
Thanks bro got it.
Basically, it’s the same