Minimum Number of Operations to Convert Time
This problem involves converting one 24hour time to another using the minimum number of operations. In one operation, you can increase the current time by 1, 5, 15, or 60 minutes. You are given two strings, current
and correct
, representing the starting and target times respectively. Your task is to figure out the minimum number of operations required to change current
into correct
.
Let’s break down the problem:
Convert both
current
andcorrect
from “HH:MM” format to total minutes past midnight. This makes the difference calculation straightforward.Calculate the difference in minutes between
correct
andcurrent
. This gives the total minutes we need to add tocurrent
to getcorrect
.Determine how many operations we need to add the total minutes. We try to use as few operations as possible, so we start with the operation that adds the most minutes: 60 minutes. Count how many 60minute operations we can perform, then do the same for 15minute operations, 5minute operations, and finally 1minute operations.


This code works by greedily using the operations that add the most minutes first. It has a time complexity of O(1), as the number of operations does not depend on the size of the input. The space complexity is also O(1), as we only use a fixed amount of space.