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# Minimum Number of Platforms

Contributed by
Deep Mavani
Medium
0/80
30 mins
70 %
+22 more

## Problem Statement

#### Your task is to find the minimum number of platforms required for the railway station so that no train needs to wait.

##### Note :
``````1. Every train will depart on the same day and the departure time will always be greater than the arrival time. For example, A train with arrival time 2240 and departure time 1930 is not possible.

2. Time will be given in 24H format and colons will be omitted for convenience. For example, 9:05AM will be given as "905", or 9:10PM will be given as "2110".

3. Also, there will be no leading zeroes in the given times. For example, 12:10AM will be given as β10β and not as β0010β.
``````
Detailed explanation ( Input/output format, Notes, Images )
##### Constraints:
``````1 <= T <= 10
1 <= N <= 50000
0 <= AT[i] <= DT[i] <= 2359

Where 'AT[i]' and 'DT[i]' are the elements of the arrival and the departure arrays respectively.

Time limit: 1 sec
``````
##### Sample Input 1:
``````2
6
900 940 950 1100 1500 1800
910 1200 1120 1130 1900 2000
4
100 200 300 400
200 300 400 500
``````
##### Sample Output 1:
``````3
2
``````
##### Explanation of the Sample Output 1:
``````In test case 1, For the given input, the following will be the schedule of the trains:

Train 1 arrived at 900 on platform 1.
Train 1 departed at 910 from platform 1.
Train 2 arrived at 940 on platform 1.
Train 3 arrived at 950 on platform 2 (since platform 1 was already occupied by train 1).
Train 4 arrived at 1100 on platform 3 (since both platforms 1 and 2 were occupied by trains 2 and 3 respectively).
Train 3 departed at 1120 from platform 2 (platform 2 becomes vacant).
Train 4 departed at 1130 from platform 3 (platform 3 also becomes vacant).
Train 2 departed at 1200 from platform 1 (platform 1 also becomes vacant).
Train 5 arrived at 1500 on platform 1.
Train 6 arrived at 1800 on platform 2.
Train 5 departed at 1900 from platform 1.
Train 6 departed at 2000 from platform 2.

Thus, minimum 3 platforms are needed for the given input.

In test case 2, For the given input, the following will be the schedule of the trains:

Train 1 arrived at 100 on platform 1.
Train 2 arrived at 200 from platform 2 (as platform 1 is occupied by train 1).
Train 1 departed at 200 from platform 1.
Train 3 arrived at 300 on platform 1.
Train 2 departed at 300 from platform 2.
Train 4 arrived at 400 on platform 2.
Train 3 departed at 400 from platform 1.
Train 4 departed at 500 from platform 2.

Thus, 2 platforms are needed for the given input.
``````
##### Sample Input 2:
``````2
2
900 1000
999 1100
3
1200 1300 1450
1310 1440 1600
``````
##### Sample Output 2:
``````1
2
``````
##### Explanation of the Sample Output 2:
``````In test case 1, For the given input, the following will be the schedule of the trains:

Train 1 arrived at 900 on platform 1.
Train 1 departed at 999 from platform 1.
Train 2 arrived at 1000 on platform 1.
Train 2 arrived at 1100 on platform 1.

Thus, only 1 platform is needed for the given input.

In test case 2, For the given input, the following will be the schedule of the trains:

Train 1 arrived at 1200 on platform 1.
Train 2 arrived at 1300 on platform 2. (since platform 1 was already occupied by train 1).
Train 1 departed at 1310 from platform 1.
Train 2 departed at 1440 from platform 2.
Train 3 arrived at 1450 on platform 1.
Train 3 departed at 1600 on platform 1.

Thus, minimum 2 platforms are needed for the given input.
``````
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