Problem
There are N intervals in which a particular integer can be chosen. What is the maximum possible minimum gap between each integer if one integer is chosen for each of those intervals?
For example: Input: [2,4], [0,8], [3,15], [10,20]
We shall choose 2 in [2,4], 8 in [0,8], 14 in [3,15], 20 in [10,20]
Thus answer is 6. The distances between the integers need not be equal. We just need to maximize the minimum of those distance.
My effort
I'm supposed to use a greedy algorithm here (mentioned in the question) but I can't get what do I do. I thought of sorting them according to the finishing time and then trying L = (maximum_range)/(N-1) as the first guess and starting from the first interval starting time I choose the next one at previous+L. If that is beyond the finishing time of the next one, I choose the finishing time and change the value of L to the new minimum (finishing_time - previous). If that is before starting time, I choose the starting time, else I choose the time previous+L itself. But this is not working in some cases like this: [2,4], [0,8], [3,9], [10,20] where it is choosing 2, 8, 9, 10 and giving the answer as 1. But the answer should be 4, where we choose 4, 0, 9, 13 respectively. I think my problem is with ordering them according to their finishing times, that fixes the element I start with, but in this case, the optimal solution does not start with [2,4] (least finishing time) itself, it should start with [0,8]. Sorting according to starting time also does not do anything.
