Problem p02759 (python)

Fixed submission:
print((int(input())+1)//2)

Buggy submission (verdict: Runtime Error):
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())
import sys
input=sys.stdin.readline
n,m,k = map(int,input().split())
ab = [list(map(int,input().split())) for i in range(m)]
cd = [list(map(int,input().split())) for i in range(k)]
num = [0]*(n+1)
g = [[] for i in range(n+1)]
uf = UnionFind(n+1)
for a,b in ab:
  g[a].append(b)
  g[b].append(a)
  uf.union(a,b)
for c,d in cd:
  if uf.same(c,d) == True:
    g[c].append(d)
    g[d].append(c)
for i in range(1,n+1):
  print(uf.size(i)-len(g[i])-1,end=" ")

Buggy submission (verdict: Runtime Error):
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())
import sys
input=sys.stdin.readline
n,m,k = map(int,input().split())
ab = [list(map(int,input().split())) for i in range(m)]
cd = [list(map(int,input().split())) for i in range(k)]
num = [0]*(n+1)
g = [[] for i in range(n+1)]
uf = UnionFind(n+1)
for a,b in ab:
  g[a].append(b)
  g[b].append(a)
  uf.union(a,b)
for c,d in cd:
  if uf.same(c,d) == True:
    g[c].append(d)
    g[d].append(c)
for i in range(1,n+1):
  print(uf.size(i)-len(g[i])-1,end=" ")