Returns minimum time difference from a given list of HH:mm time entries

getMinTimeDifference.java

   public long getMinDifferenceInMinutes(String[] journal){
        if(journal == null) return 0;

        if(journal.length == 0) return 0;

        //Using a set to store unique and valid entries
        //if any entry is duplicated, it will auto break because that will be the minimum time difference
        //TreeSet stores data in natural order - O(Log N) time complexity - better than sorting array with NLogN
        //sorting keeps times close together and will eliminate comparing each entry with all other elements
        //Tradeoff extra space for faster sort process
        Set<Long> validEntries = new TreeSet<>();

        //based on requirement, journal entries are in HH:MM - 24hr format
        SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm");

        //strip out invalid entries and put the rest in the tree set - O(N)
        for(int index = 0; index < journal.length; index++){
            try {
                long timeInMs = dateFormat.parse(journal[index]).getTime();
                if(validEntries.contains(timeInMs)) return 0;
                validEntries.add(timeInMs);
            } catch (ParseException e) {
                //String is in a wrong format - ignore
                continue;
            }
        }

        //no valid entries after the filter
        if(validEntries.size() == 0) return 0;


        //find difference - O(N) worst case
        long prev = Long.MIN_VALUE;
        long diff = Long.MIN_VALUE;
        for(long entry : validEntries){
            if(prev != Long.MIN_VALUE){
                long timeDiff = Math.abs(entry - prev);
                diff = (diff != Long.MIN_VALUE) ? Math.min(timeDiff, diff) : timeDiff;
            }
            prev = entry;
        }

        return (diff!=Long.MIN_VALUE) ? TimeUnit.MILLISECONDS.toMinutes(diff) : TimeUnit.MILLISECONDS.toMinutes(prev);
   }

Hello @deedee47, congratulations 🎉 your solution has been selected as one of the winning solutions in Week 7 of #AlgorithmFridays. Your solution is clean and readable and passed the test cases.

One feedback for you is, when submitting your solution, please endeavor to add the import statement for all the packages your solution uses.

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