1D Array

 /*                  Largest Number At Least Twice of Others
                    You are given an integer array nums where the largest integer is unique.
Determine whether the largest element in the array is at least twice as much as every other number in the array. 
If it is, print the index of the largest element, or print -1 otherwise.                    */

import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n =sc.nextInt();
		int a[] = new int[n];
		int max = Integer.MIN_VALUE;
		int maxindex =0;
		for(int i=0;i<n;i++){
		    a[i]=sc.nextInt();
		    if(a[i]>max){
		        max =a[i];
		        maxindex =i;
		    }
		    
		}
		boolean flag = false;
		for(int i=0;i<n;i++){
		        if( i!=maxindex && max < 2*a[i]){
		            flag = true;
		        }
		    }
		    if(flag){
		        System.out.println(-1);
		    }
		    else{
		        System.out.println(maxindex);
		    }
		
	}
}


/*     PEAK ELEMENT
An element is called a peak element if its value is not smaller than the value of its adjacent elements(if they exists). Given an array arr[] of size n, find the index of first peak element. If peak element does not exist print -1.

Input
line 1: contains an integer n denoting size of array.

line 2: contains n spaced integers denoting elements of array.

Output
Print a single integer denoting the index of first peak element in array. If no such element exists, print -1.         */
import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n =sc.nextInt();
		int a[] = new int[n];
		for(int i=0;i<n;i++){
		    a[i]=sc.nextInt();
		    
		}
    if(n==1){
    System.out.println(0);
    return;
    }
		if(a[0]>a[1] ){
		    System.out.println(0);
		    return;
		}
		
		    for(int i=1;i<n-1;i++){
		        if(a[i]>a[i+1] &&a[i]>a[i-1]){
		            System.out.println(i);
		            return;
		        }
		    }
		
		 if(a[n-1]>a[n-2]){
		     System.out.println(n-1);
		     return;
		}
		
		    System.out.println(-1);
		
	}
}
   /*  SUM OF ARRAY EXCEPT SELF  */
         import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n =sc.nextInt();
		int a[] = new int[n];
		int sum =0;
		for(int i=0;i<n;i++){
		    a[i]=sc.nextInt();
		    sum += a[i];
		    
		}
		for(int i=0;i<n;i++){
		    System.out.print(sum-a[i] +" ");
		}
		
		
	}
}
          // largest and second largest number in an array

        import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n =sc.nextInt();
		int a[] = new int[n];
		int max =Integer.MIN_VALUE;
		int secondmax = Integer.MIN_VALUE;
		for(int i=0;i<n;i++){
		    a[i]=sc.nextInt();
		    if(a[i]>max){
		        secondmax = max;
		        max = a[i];
		    }
		    else if(a[i]>secondmax){
		        secondmax =a[i];
		    }
		}
		
		System.out.println(max);
		System.out.println(secondmax);
		
	}
}


         /*Given a sorted array A and a target value B, return the index if the target is found. If not, print the index where
	 it would be if it were inserted in order.
	 First line given is an integer N, denoting the size of array A. Second line contains N integers - the elements of array A. 
	 Third line given is integer B.
	 example 4 [3 7 12 44]  11   output 2(index number)                    */
	 
	 import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n =sc.nextInt();
		int a[] = new int[n];
		for(int i=0;i<n;i++){
		    a[i]=sc.nextInt();
		    
		}
		int k = sc.nextInt();
		for(int i=0;i<n;i++){
		    if(a[i]>=k){
		        System.out.println(i);
		        break;
		    }
		    
		}
	}
}
	   /*           Find First and Last Position of Element in Sorted Array
           Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.

         If target is not found in the array, print[-1, -1].            */
	 
	 
	 import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner sc = new Scanner(System.in);
      int n =sc.nextInt();
      int k =sc.nextInt();
      int a[] = new int[n];
      for(int i=0;i<n;i++){
        a[i] =sc.nextInt();
      }
      int ans1 = -1;
      for(int i=0;i<n;i++){
        if(a[i]==k){
          ans1 =i;
          break;
        }
      }
      System.out.print(ans1 +" ");
      int ans2 =-1;
      
            for(int i=n-1;i>=0;i--){
        if(a[i]==k){
          ans2 = i;
          break;
        }
      }
      
      System.out.print(ans2);
	}
}