{

public static List<List<Integer>> diagonalTraversal( int[][] A )

{

List<List<Integer>> result = new ArrayList<>();

int N = A.length;

int M = A[0].length;

int count = 0;

for( int i = 0; i < M; i++ )

{

count++;

int row = 0;

int col = i;

List<Integer> currentResult = new ArrayList<>();

while( row < N && col >= 0 )

{

currentResult.add( A[row][col] );

row++;

col--;

}

if( count % 2 != 0 )

Collections.reverse( currentResult );

result.add( currentResult );

}

for(int i=1;i<M;i++)

{

count++;

int row=i;

int col = N-1;

List<Integer> currentResult = new ArrayList<>();

while(row<M && col>0)

{

currentResult.add( A[row][col] );

row++;

col--;

}

if(count%2!=0)

Collections.reverse( currentResult );

result.add( currentResult );

}

return result;

}

public static void main( String[] args )

{

int[][] A = new int[][]{ { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 }, { 13, 14, 15, 16 } };

System.out.println( diagonalTraversal( A ) );

}