Python Program for Activity Selection Problem | Greedy Algo-1

You are given n activities with their start and finish times. Select the maximum number of activities that can be performed by a single person, assuming that a person can only work on a single activity at a time.
Example:

Example 1 : Consider the following 3 activities sorted by
by finish time.
     start[]  =  {10, 12, 20};
     finish[] =  {20, 25, 30};
A person can perform at most two activities. The 
maximum set of activities that can be executed 
is {0, 2} [ These are indexes in start[] and 
finish[] ]

Example 2 : Consider the following 6 activities 
sorted by by finish time.
     start[]  =  {1, 3, 0, 5, 8, 5};
     finish[] =  {2, 4, 6, 7, 9, 9};
A person can perform at most four activities. The 
maximum set of activities that can be executed 
is {0, 1, 3, 4} [ These are indexes in start[] and 
finish[] ]

Python

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"""The following implementation assumes that the activities
are already sorted according to their finish time"""
  
"""Prints a maximum set of activities that can be done by a
single person, one at a time"""
# n --> Total number of activities
# s[]--> An array that contains start time of all activities
# f[] --> An array that contains finish time of all activities
  
def printMaxActivities(s, f ):
    n = len(f)
    print "The following activities are selected"
  
    # The first activity is always selected
    i = 0
    print i,
  
    # Consider rest of the activities
    for j in xrange(n):
  
        # If this activity has start time greater than
        # or equal to the finish time of previously
        # selected activity, then select it
        if s[j] >= f[i]:
            print j,
            i = j
  
# Driver program to test above function
s = [1, 3, 0, 5, 8, 5]
f = [2, 4, 6, 7, 9, 9]
printMaxActivities(s, f)
  
# This code is contributed by Nikhil Kumar Singh

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Output:

The following activities are selected
0 1 3 4

Please refer complete article on Activity Selection Problem | Greedy Algo-1 for more details!



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