a_145_Activity_Selection.java

import java.util.*;


public class a_145_Activity_Selection {
    public static void main(String[] args) {
        int start[] = {1, 3, 0, 5, 8, 5 } ;
        int end[] = {2, 4, 6, 7, 9, 9 } ;

        // end time basis sorted 
        // int maxAct = 0 ;
        // ArrayList<Integer> ans = new ArrayList<>() ;
        
        // // 1st activity 
        // maxAct = 1 ;
        // ans.add(0)  ;
        // int lastEnd = end[0] ;

        // for(int i=0; i<end.length; i++){
        //     if(start[i] >= lastEnd) {
        //         // Activity select
        //         maxAct++ ;
        //         ans.add(i) ;
        //         lastEnd = end[i] ;
        //     }
        // }

        // System.out.println("Maximum Activity are = " + maxAct );

        // for(int i=0; i<ans.size() ; i++){
        //     System.out.print("A"+ ans.get(i) +" ");
        // }
        //   System.out.println() ;

        
        // if end[] are not sorted given
        // sorting 
        int activities[][] = new int[start.length][3] ;
        for(int i=0; i<start.length; i++) {
            activities[i][0] = i ;
            activities[i][1] = start[i]  ;
            activities[i][2] = end[i]  ;
        }

        // lambda function - shortform 
        Arrays.sort(activities, Comparator.comparingDouble( o -> o[2] ) ) ;

        int maxAct = 0 ;
        ArrayList<Integer> ans = new ArrayList<>() ;
        
        //  1st activity 
        maxAct = 1 ;
        ans.add(activities[0][0])  ;
        int lastEnd = activities[0][2] ;

        for(int i=0; i<end.length; i++){
            if(activities[i][1] >= lastEnd) {
                 // Activity select
                maxAct++ ;
                ans.add(activities[i][0]) ;
                lastEnd = activities[i][2] ;
            }
        }

        System.out.println("Maximum Activity are = " + maxAct );

        for(int i=0; i<ans.size() ; i++){
            System.out.print("A"+ ans.get(i) +" ");
        }
          System.out.println() ;

    
    }
}