Formatted question description: https://leetcode.ca/all/1904.html

# 1904. The Number of Full Rounds You Have Played

## Level

Medium

## Description

A new online video game has been released, and in this video game, there are **15-minute** rounds scheduled every **quarter-hour** period. This means that at `HH:00`

, `HH:15`

, `HH:30`

and `HH:45`

, a new round starts, where `HH`

represents an integer number from `00`

to `23`

. A **24-hour clock** is used, so the earliest time in the day is `00:00`

and the latest is `23:59`

.

Given two strings `startTime`

and `finishTime`

in the format `"HH:MM"`

representing the exact time you **started** and **finished** playing the game, respectively, calculate the **number of full rounds** that you played during your game session.

- For example, if
`startTime = "05:20"`

and`finishTime = "05:59"`

this means you played only one full round from`05:30`

to`05:45`

. You did not play the full round from`05:15`

to`05:30`

because you started after the round began, and you did not play the full round from`05:45`

to`06:00`

because you stopped before the round ended.

If `finishTime`

is **earlier** than `startTime`

, this means you have played overnight (from `startTime`

to the midnight and from midnight to `finishTime`

).

Return *the number of full rounds that you have played if you had started playing at startTime and finished at finishTime*.

**Example 1:**

**Input:** startTime = “12:01”, finishTime = “12:44”

**Output:** 1

**Explanation:** You played one full round from 12:15 to 12:30.

You did not play the full round from 12:00 to 12:15 because you started playing at 12:01 after it began.

You did not play the full round from 12:30 to 12:45 because you stopped playing at 12:44 before it ended.

**Example 2:**

**Input:** startTime = “20:00”, finishTime = “06:00”

**Output:** 40

**Explanation:** You played 16 full rounds from 20:00 to 00:00 and 24 full rounds from 00:00 to 06:00.

16 + 24 = 40.

**Example 3:**

**Input:** startTime = “00:00”, finishTime = “23:59”

**Output:** 95

**Explanation:** You played 4 full rounds each hour except for the last hour where you played 3 full rounds.

**Constraints:**

`startTime`

and`finishTime`

are in the format`HH:MM`

.`00 <= HH <= 23`

`00 <= MM <= 59`

`startTime`

and`finishTime`

are not equal.

## Solution

If the finish time is less than the start time, add 24 hours to the finish time. Next find the smallest time greater than or equal to `startTime`

that has minutes as a multiple of 15, and find the largest time less than or equal to `finishTime`

that has minutes as a multiple of 15. Then calculate the time range between the start time and the end time. Divide the time range by 15 to get the number of full rounds. The number of full rounds must be non-negative, so if the calculated number of full rounds is negative, return 0.

```
class Solution {
public int numberOfRounds(String startTime, String finishTime) {
int startHour = Integer.parseInt(startTime.substring(0, 2)), startMinute = Integer.parseInt(startTime.substring(3));
int finishHour = Integer.parseInt(finishTime.substring(0, 2)), finishMinute = Integer.parseInt(finishTime.substring(3));
if (finishHour < startHour || finishHour == startHour && finishMinute < startMinute)
finishHour += 24;
if (startMinute % 15 != 0) {
startMinute = startMinute - startMinute % 15 + 15;
if (startMinute == 60) {
startHour++;
startMinute = 0;
}
}
if (finishMinute % 15 != 0)
finishMinute -= finishMinute % 15;
int minutesBetween = (finishHour - startHour) * 60 + (finishMinute - startMinute);
minutesBetween = Math.max(minutesBetween, 0);
int rounds = minutesBetween / 15;
return rounds;
}
}
```