/**

Give a N*N square matrix, return an array of its anti-diagonals. Look at the example for more details.

Example:

Input:

1 2 3

4 5 6

7 8 9

Return the following :

[

[1],

[2, 4],

[3, 5, 7],

[6, 8],

[9]

]

Input :

1 2

3 4

Return the following :

[

[1],

[2, 3],

[4]

]

*/

public class Solution {

public ArrayList<ArrayList<Integer>> diagonal(ArrayList<ArrayList<Integer>> a) {

int len = a.get(0).size();

int i = 0;

int j = 0;

int l = 0;

ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();

for(l=0; l < len; l++){

ArrayList<Integer> iR = new ArrayList<Integer>();

for(i=l;i>=0;i--){

iR.add(a.get(l-i).get(i));

}

res.add(iR);

}

l = len - 1 ;

for(i=0;i<l;i++){

ArrayList<Integer> iR = new ArrayList<Integer>();

for(j=0;j+i<l;j++){

iR.add(a.get(i+j+1).get(l-j));

}

res.add(iR);

}

return res;

}

}