Example 1:
Input: m = 3, n = 3, positions = [[0,0],[0,1],[1,2],[2,1],[1,1]]
Output: [1,1,2,3,1]
Explanation:
Example 2:
Input: m = 1, n = 1, positions = [[0,0]]
Output: [1]
You are given an empty m x n grid initially filled with water. We may perform an addLand operation where positions[i] = [ri, ci] turns the cell (ri, ci) into land.
Return an array answer where answer[i] is the number of islands after the ith operation.
An island is a maximal group of horizontally or vertically adjacent land cells.
The last addition connects three previously separate islands into one.
1 <= m, n <= 10^41 <= m * n <= 10^40 <= positions.length <= 10^40 <= ri < m0 <= ci < n