2dmatrixPatterPrint01

/* "static void main" must be defined in a public class.


*/
public class Main {
    public static void main(String[] args) {
        System.out.println("Hello World!");
        Main main = new Main();
        int[][] arr = new int[][]{
            // {1,2,3,4,5,6,7,8},
            // {6,7,8,9,10},
            // {11,12,13,14,15},
            // {16,17,18,19,20}


            {1,2,3,4,5},
            {6,7,8,9,10},
            {11,12,13,14,15},
            {16,17,18,19,20}
        };
        main.action(arr);
        main.spiralPrint(arr);
    }
    public void spiralPrint(int[][] arr){
        int height = arr.length;
        int width = arr[0].length;
        int cs = 0;
        int ce = width-1;
        int rs = 0;
        int re = height-1;
        int i,j;
        while(rs < re && cs < ce){

            j=cs;
            i=rs;
            while(j <= ce){
                System.out.print(String.format("%s ",arr[i][j]));
                j++;
            }
            rs+=1;
            i=rs;
            j=ce;
            while(i <= re){
                System.out.print(String.format("%s ",arr[i][j]));
                i++;
            }
            ce-=1;
            i=re;
            j=ce;
            while(j>=cs){
                System.out.print(String.format("%s ",arr[i][j]));
                j--;
            }
            re-=1;
            i=re;
            j=cs;
            while(i>=rs){
                System.out.print(String.format("%s ",arr[i][j]));
                i--;
            }
            cs+=1;
        }
    }
    public void action(int [][] arr){
        // print diagonal in zig - zag pattern
        /*
        [1]
        [6, 2]
        [3, 7, 11]
        [16, 12, 8, 4]
        [5, 9, 13, 17]
        [18, 14, 10]
        [15, 19]
        [20]
        */
        int width = arr.length;
        int height =arr[0].length;
       List[] arli = new List[width+height-1];
        for(int i=0;i<width;++i){
            for(int j=0;j<height;++j){
                if(arli[i+j] == null){
                    arli[i+j] = new ArrayList();
                }
                arli[i+j].add(arr[i][j]);
            }
        }
        int count=0;
        for(List li : arli){
            if(count%2==1)
                Collections.reverse(li);
            System.out.println(li);

            count++;
        }
    }

}