First Index And Last Index

 1. You are given a number n, representing the size of array a.

2. You are given n numbers, representing elements of array a.

Asssumption - Array is sorted. Array may have duplicate values.

Input Format

A number n
n1
n2
.. n number of elements
A number d

Output Format

A number representing first index
A number representing last index

Constraints
1 <= n <= 1000
1 <= n1, n2, .. n elements <= 100
1 <= d <= 100
Sample Input
15
1
5
10
15
22
33
33
33
33
33
40
42
55
66
77
33
Sample Output
5
9

import java.io.*;
import java.util.*;

public class Main{

public static void main(String[] args) throws Exception {
    // write your code here
    Scanner scn = new Scanner(System.in);
    int n = scn.nextInt();
    int[] A = new int[n];
    for(int i=0;i<n;i++)
        A[i] =scn.nextInt();
    int d = scn.nextInt();
    
    System.out.println(binarySearch(0,n-1,A,d,true));
    System.out.println(binarySearch(0,n-1,A,d,false));
 }

  public static int binarySearch(int lt, int rt,int[] A, int d, boolean findFirst){
      int pos = -1;
      while(lt<=rt){
        int mid = (lt+rt)/2;
        if(A[mid]<d)
            lt = mid + 1;
        else if(A[mid]>d)
            rt = mid - 1;
        else{
            pos = mid;
            if(findFirst)
                rt = mid - 1;
            else 
                lt = mid + 1;
        }
     }
     return pos;
  }

}