ReverseSpiral

import java.util.*; // importing packages
public class Spiralmatrix  // This Code is Written by Sameer Trpathi
{// start of class
    public static void main()
    { // start of main
        Scanner sc = new Scanner(System.in);
        System.out.println("ENTER THE NUMBER ="); // taking input by the user 
        int n = sc.nextInt();
        int [][]m= new int [n][n]; // forming matrix of n X n 
        int cs=0; // marking start index of column 
        int ce=n-1; // marking end index of column 
        int rs=0; // marking start index of row
        int re=n-1; // marking start index  of row 
        int num = n*n; // storing the number to print in reverse order .
        
        
        
        while (cs<=ce && rs<=re) // this loop helps to fill element in spiral order
        {// start of while loop 

            // Moving right 
            for(int i = cs;i<=ce;i++) // loop to input value in upper boundary 
            {
                m[rs][i] = num--;// storing the value in reverse order in upper most boundary of column .
            }
            rs++; // shifting row control to 2nd row to print left element from 2nd row in lastr column  

            // moving down 
            for(int i = rs;i<=re;i++)// loop to input value in right boundary of matrix 
            { 
                m[i][ce]=num--;// storing the value in reverse order in right boundary of matrix
            }
            ce--;// shifting column control to 2nd last column to print elements in lower boundary of matrixfrom left to right

            // moving left
            if(rs<=re) // checking if the control is not going out of bound in row indexes 
            {    for(int i=ce;i>=cs;i--)// loop to input value in down boundary of matrix
                {
                    m[re][i]=num--;// storing the value in reverse order in down boundary of matrix
                }
            }
            re--; //decreasing rowend index by 1 to direction the print upward   

            //moving up
            if(cs<=ce) // checking if the control is not going out of bound in column indexes
            {  for(int i= re;i>=rs;i--)// loop to input value in left boundary of matrix
                { m[i][cs]=num--; // storing the value in reverse order in left boundary of matrix
                }
            }
            cs++;//increase column index by 1 to direction the print in spiral form by turning control inward from left to right .

        } // end of while loop

        //loop to print the spiral 
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<n;j++)
            {
                System.out.print(m[i][j]+"\t");
            }
            System.out.println();
        }

    }// end of main
}// end of class