LC1904.java

class Solution {
    private int getStartMinuteRoundUp(int min) {
        if (min % 15 == 0) return min;
        if (min > 0 && min < 15) return 15;
        if (min > 15 && min < 30) return 30;
        if (min > 30 && min < 45) return 45;
        return 0;
    }
    
    private int getFinishMinuteRoundUp(int min) {
        if (min % 15 == 0) return min;
        if (min > 0 && min < 15) return 0;
        if (min > 15 && min < 30) return 15;
        if (min > 30 && min < 45) return 30;
        return 45;
    }
    
    private boolean isNextHour(int min) {
        String minute = String.valueOf(min);
        if (minute.length() == 1) return false;
        if (minute.length() == 2) return minute.charAt(0) == '6';
        if (minute.length() == 3) return minute.charAt(1) == '6';
        else return minute.charAt(2) == '6';
    }
    
    public int numberOfRounds(String startTime, String finishTime) {
        String[] s = startTime.split(":");
        String[] f = finishTime.split(":");
        int start = 0, finish = 0;
        
        int startHour = Integer.parseInt(s[0]);
        int startMinute = Integer.parseInt(s[1]);
        int finishHour = Integer.parseInt(f[0]);
        int finishMinute = Integer.parseInt(f[1]);
        if ((startHour * 100 + startMinute) > ((finishHour * 100) + finishMinute)) finish += 2400;
        
        int mStartMinute = getStartMinuteRoundUp(Integer.parseInt(s[1]));
        if (mStartMinute != startMinute) {
            startMinute = mStartMinute;
            startHour = mStartMinute == 0 ? startHour + 1 : startHour;
        }
        
        int mFinishMinute = getFinishMinuteRoundUp(Integer.parseInt(f[1]));
        if (mFinishMinute != finishMinute) {
            finishMinute = mFinishMinute;
        }
        
        start = startHour * 100 + startMinute;
        finish += (finishHour * 100 + finishMinute);
        int numOfRounds = 0;
        while (start < finish) {
            ++numOfRounds;
            start += 15;
            if (isNextHour(start)) {
                start = ((start / 100) + 1) * 100;
            }
        }
        return numOfRounds;
    }
}