_539.java

package com.fishercoder.solutions;

import java.util.List;

/**
 * Given a list of 24-hour clock time points in "Hour:Minutes" format, find the minimum minutes difference between any two time points in the list.

 Example 1:
 Input: ["23:59","00:00"]
 Output: 1

 Note:
 The number of time points in the given list is at least 2 and won't exceed 20000.
 The input time is legal and ranges from 00:00 to 23:59.
 */
public class _539 {

    public int findMinDifference(List<String> timePoints) {
//        there are in total 24*60 = 1440 possible time points
        final int ALL_POSSIBLE_TIMEPOINTS = 1440;
        boolean[] allTimePoints = new boolean[ALL_POSSIBLE_TIMEPOINTS];
        for (String eachTime : timePoints) {
            String[] timeParts = eachTime.split(":");
            int hour = Integer.valueOf(timeParts[0]);
            int minute = Integer.valueOf(timeParts[1]);
            int value = hour * 60 + minute;
            if (allTimePoints[value]) {
                return 0;
            }
            allTimePoints[value] = true;
        }

        int min = Integer.MAX_VALUE;
        int prev = 0;
        int first = Integer.MAX_VALUE;
        int last = Integer.MIN_VALUE;
        for (int i = 0; i < ALL_POSSIBLE_TIMEPOINTS; i++) {
            if (allTimePoints[i]) {
                if (first != Integer.MAX_VALUE) {
                    min = Math.min(min, i - prev);
                }
                first = Math.min(first, i);
                last = Math.max(last, i);
                prev = i;
            }
        }
        min = Math.min(min, (ALL_POSSIBLE_TIMEPOINTS - last + first));
        return min;
    }

}