Minimum Time Difference

LeetCode Q 539 - Minimum Time Difference

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.

Solution:

First sort the list. The minimum time difference can only happen between two adjacent times or between the first and last time.

Code:

public int findMinDifference(List<String> timePoints) {
  
  Collections.sort(timePoints);
  
  int l = 0, r = timePoints.size() - 1;
  int res = change2Mins(timePoints.get(l)) + 24 * 60 - change2Mins(timePoints.get(r));
  
  while (l <= r - 1) {
    int lmins1 = change2Mins(timePoints.get(l));
    int lmins2 = change2Mins(timePoints.get(l + 1));
    if (lmins2 - lmins1 < res) res = lmins2 - lmins1;
    l++;
  }
  
  return res;
}

private int change2Mins(String time) {
  int mins = Integer.parseInt(time.substring(3, 5));
  int hours = Integer.parseInt(time.substring(0, 2));
  return hours * 60 + mins;
}