Size of Islands

Given a 2d grid map of 1s (land) and 0s (water), find the islands and return a list containing their sizes. An island is surrounded by water and is formed by connecting adjacent land cells horizontally or vertically. You may assume all four edges of the grid are surrounded by water.

Example 1:

Input:
1 1 1 1 0
1 1 0 1 0
1 1 0 0 0
0 0 0 0 0

Output: [9]
Explanation:  There is only one island with size 9

Example 2:

Input:
1 1 0 0 0
1 1 0 0 0
0 0 1 0 0
0 0 0 1 1

Output: [1, 4, 2]
Explanation There are three islands with sizes of 1, 4 and 2