Added minimum platforms required problem

greedy_methods/minimum_platforms_required.py

@@ -0,0 +1,53 @@
+"""
+This is a pure Python implementation of the greedy algorithm
+reference: https://practice.geeksforgeeks.org/problems/minimum-platforms-1587115620/1#
+
+For doctests run following command:
+python3 -m doctest -v minimum_platforms_required.py
+
+We will sort both arrays. When there is sorted events, it will be easy to maintain
+the count of trains that have arrived but not departed. The total platforms needed
+at one time can be found by taking the difference between arrivals and departures
+minimum will be the final answer.
+"""
+
+
+def minimum_platforms_required(arrival_times, departure_times):
+    """Function to count the minimum number of platforms required.
+
+    Args:
+        arrival_times (list): List of arrival times.
+        departure_times (list): List of departure times.
+
+    Returns:
+        int: Minimum number of platforms required.
+
+    Examples:
+    >>> minimum_platforms_required([900, 945, 955, 1100, 1500, 1800],
+    ...                            [920, 1200, 1130, 1150, 1900, 2000])
+    3
+    """
+    arrival_times.sort()
+    departure_times.sort()
+
+    platforms_needed = 1
+    count = 1
+    i = 1
+    j = 0
+
+    while i < len(arrival_times) and j < len(departure_times):
+        if arrival_times[i] <= departure_times[j]:  # one more platform needed
+            count += 1
+            i += 1
+        else:  # one platform can be reduced
+            count -= 1
+            j += 1
+        platforms_needed = max(platforms_needed, count)
+
+    return platforms_needed
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()