Car Fleet ​
Cars travel towards the same destination at different speeds and cannot overtake; count how many distinct fleets arrive.
Approach ​
Sort the values by position descendng. Calculate the eta they arrive at. If stack is empty or top of stack has a value less than eta, push to stack. return count of stack.
Better way: Sort, while iterating, check if prevETA is bigger than current, then set fleet++. Return fleet.