C# 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 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 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[] ]

C#

// The following implementation assumes
// that the activities are already sorted
// according to their finish time
using System;

class GFG {
    // 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
    public static void printMaxActivities(int[] s,
                                          int[] f, int n)
    {
        int i, j;

        Console.Write("Following activities are selected : ");

        // The first activity always gets selected
        i = 0;
        Console.Write(i + " ");

        // Consider rest of the activities
        for (j = 1; j < n; j++) {
            // 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]) {
                Console.Write(j + " ");
                i = j;
            }
        }
    }

    // Driver Code
    public static void Main()
    {
        int[] s = { 1, 3, 0, 5, 8, 5 };
        int[] f = { 2, 4, 6, 7, 9, 9 };
        int n = s.Length;

        printMaxActivities(s, f, n);
    }
}

// This code is contributed
// by ChitraNayal

Output:

Following activities are selected : 0 1 3 4

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