Editorialist: Karan Aggarwal
The problem requires you to simulate the running of 2 players with different speed P and Q around a stadium for S seconds each, and tell the number of time they will meet.
The stadium is in form of a line with M-1 pillars and then a loop with N-M+1 pillars, thus a total of N pillars. The limits of S are such that a O(S) solution will pass the time limits. Also, given a current position and speed, the next position of the player can be found in O(1) by simple mathematics.
new_pillarPosition = M + (current_pillarPosition + speed - M) % (N-M+1)
To reach to this formula, we have to observe that there is a cycle of length (N-M+1), but a extra M is present in the pillar position, which we can remove, then add the speed and find the new position in the cycle by taking a MOD with cycle length, then add M again, to get the actual pillar number.