Diagonal Traverse

class Solution {
    public int[] findDiagonalOrder(int[][] matrix) {
        if(matrix.length == 0){
            return new int[]{};
        }
        int[][] u = new int[matrix.length * matrix[0].length][3];
        int[] u1 = new int[matrix.length*matrix[0].length];
        int c = 0;
        int max = 1;
        int count = 0;
        for(int i = 0; i<matrix.length; i++){
            for(int j = 0; j<matrix[0].length; j++){
                u[c++] = new int[]{i+j, j, matrix[i][j]};
            }
        }
        Arrays.sort(u, new Comparator<int[]>() {
				public int compare(int[] a, int[] b) {
					if(a[0] != b[0]){
                        return a[0] - b[0];
                    }
                    if(a[0]%2!=0){
                        return -(a[1]-b[1]);
                    }
					return a[1] - b[1];
				}
			});
        //System.out.println(Arrays.deepToString(u));
        for(int i = 0; i<u1.length; i++){
            u1[i] = u[i][2];
        }
        return u1;
    }
}