947. Most Stones Removed with Same Row or Column

#.    . .
#.  .   .
#.  . .
class Solution:
    def removeStones(self, stones: List[List[int]]) -> int:

        n = len(stones)

        if n == 1:
            return 0

        parents = {}

        def find(x):
            if x not in parents:
                parents[x] = x
            if x != parents[x]:
                parents[x] = find(parents[x])
            return parents[x]

        def union(x, y):
            x = find(x)
            y = find(y)
            if x < y:
                parents[y] = x
            else:
                parents[x] = y

        for i in range(n):
            find(i)

        for i in range(n):
            for j in range(i):
                if stones[i][0] == stones[j][0]:
                    union(i, j)
                if stones[i][1] == stones[j][1]:
                    union(i, j)

        for i in range(n):
            find(i)


        return len(parents) - len(set(parents.values()))