PROBLEM LINKS
DIFFICULTY
MEDIUM
EXPLANATION
Notice the following 2 observations
- The postmen can be considered as if they are passing through each other
- The relative position of a postman never changes
Using the first we can calculate the final positions by just adding or subtracting the time from the initial positions depending on the direction being South or North. Combining this with 2, we can easily see that if we sort the final positions, we will get the position of the the respective postman. But we also have to calculate the collisions. For that we can do the sorting of the positions using Bubble Sort where each swapping of adjacent numbers in the array means a collision. And, hence we can easily count the same.
SETTER’S SOLUTION
Can be found here.
TESTER’S SOLUTION
Can be found here.