Problem p02762 (python)

Fixed submission:
import sys
input = sys.stdin.buffer.readline

# https://note.nkmk.me/python-union-find/
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())


N, M, K = map(int, input().split())
uf = UnionFind(N)

n_friend = [0]*N
for i in range(M):
    a, b = map(int, input().split())
    uf.union(a-1, b-1)
    n_friend[a-1] += 1
    n_friend[b-1] += 1

n_block_in_friend_cluster = [0]*N
for i in range(K):
    c, d = map(int, input().split())
    if uf.same(c-1, d-1):
        n_block_in_friend_cluster[c-1] += 1
        n_block_in_friend_cluster[d-1] += 1

ans = [uf.size(i) - n_friend[i] - n_block_in_friend_cluster[i] - 1 for i in range(N)]
print(*ans)

Buggy submission (verdict: Runtime Error):
class UnionFind(object):
    def __init__(self, n=1):
        self.root = [i for i in range(n)]
        self.rank = [0 for _ in range(n)]

    def find(self, x):
        if self.root[x] == x:
            return x
        else:
            self.root[x] = self.find(self.root[x])
            return self.root[x]

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                x, y = y, x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
            self.root[y] = x

    def is_same_root(self, x, y):
        return self.find(x) == self.find(y)


N, M, K = map(int, input().split())
uf1 = UnionFind(N)

friend = [[] for _ in range(N)]
for i in range(M):
    a, b = map(int, input().split())
    uf1.unite(a-1, b-1)
    friend[a-1].append(b-1)
    friend[b-1].append(a-1)

block = [[] for _ in range(N)]
for i in range(K):
    c, d = map(int, input().split())
    block[c-1].append(d-1)
    block[d-1].append(c-1)

for i in range(N):
    uf1.find(i)  # 一周findすることによって接続漏れをなくす

group = [None] * N
done_member = set()
for i in range(N):
    if i in done_member:
        break
    else:
        done_member.add(i)
    same_group_set = set([i])
    for j in range(N):
        if uf1.is_same_root(i,j):
            same_group_set.add(j)
            done_member.add(j)
    for k in same_group_set:
        group[k] = same_group_set

ans = [(len(group[i] - set(friend[i]) - set(block[i])) - 1) for i in range(N)]
print(*ans)