Buggy python submission (verdict: Runtime Error):
N, M = map(int, input().split())
AB = [[] for _ in range(N)]

for _ in range(M):
    a,b = map(lambda x: int(x)-1, input().split())
    AB[a].append(b)
    AB[b].append(a)

def dfs(v):
    visited[v] = 1
    for i in AB[v]:
        if visited[i]:
            continue
        dfs(i)

visited = [0]*N
cnt = 0
for i in range(N):
    if visited[i]:
        continue
    dfs(i)
    cnt += 1
print(cnt-1)

Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)

Buggy python submission (verdict: Runtime Error):
n,m = map(int,input().split())
L = [[] for _ in range(n)]

for i in range(m):
    a,b = map(lambda x:int(x)-1,input().split())
    L[a].append(b)
    L[b].append(a)
    
def dfs(i):
    if visited[i]:
        return
    visited[i] = True
    for j in L[i]:
        if visited[j]:
            continue
        dfs(j)
        
visited = [False]*n
cnt = 0

for i in range(n):
    if visited[i]:
        continue
    dfs(i)
    cnt +=1
    
print(cnt-1)

Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)

Buggy python submission (verdict: Runtime Error):
n,m = map(int,input().split())
L = [[] for _ in range(n)]

for i in range(m):
    a,b = map(lambda x:int(x)-1,input().split())
    L[a].append(b)
    L[b].append(a)
    
def dfs(i):
    visited[i] = True
    for j in L[i]:
        if visited[j]:
            continue
        dfs(j)
        
visited = [False]*n
cnt = 0

for i in range(n):
    if visited[i]:
        continue
    dfs(i)
    cnt +=1
    
print(cnt-1)

Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)

Buggy python submission (verdict: Runtime Error):
n,m = map(int,input().split())
#L = [list(map(int,input().split())) for i in range(m)]


class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a,b)
max1 = 0
for i in range(n):
    max1 = max(max1,d.size(i))
print(max1-1)


Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)

Buggy python submission (verdict: Runtime Error):
n,m = map(int,input().split())
#L = [list(map(int,input().split())) for i in range(m)]


class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parent = [i for i in range(n)]  # 親
        self.rank = [1] * n  # 木の高さ
        self.size = [1] * n  # size[i] は i を根とするグループのサイズ

    def find(self, x):  # x の根を返す
        if self.parent[x] == x:
            return x
        else:
            self.parent[x] = self.find(self.parent[x])  # 経路圧縮
            return self.parent[x]

    def unite(self, x, y):  # x, y の属する集合を併合する
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                self.parent[x] = y
                self.size[y] += self.size[x]
            else:
                self.parent[y] = x
                self.size[x] += self.size[y]
                if self.rank[x] == self.rank[y]:
                    self.rank[x] += 1

    def is_same(self, x, y):  # x, y が同じ集合に属するか判定する
        return self.find(x) == self.find(y)

    def group_size(self, x):  # x が属する集合の大きさを返す
        return self.size[self.find(x)]

    def group_members(self, x):  # x が属する集合の要素を返す
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):  # すべての根をリストで返す
        return [i for i, x in enumerate(self.parent) if i == x]

    def group_count(self):  # 木の数を返す
        return len(self.roots())

    def all_group_members(self):  # すべての木の要素を辞書で返す
        return {r: self.group_members(r) for r in self.roots()}

#a = [i+1 for i in range(n)]
d = UnionFind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.unite(a,b)

print(d.group_count()-1)

Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)

Buggy python submission (verdict: Runtime Error):
n,m = map(int,input().split())
L = [list(map(int,input().split())) for i in range(m)]


class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parent = [i for i in range(n)]  # 親
        self.rank = [1] * n  # 木の高さ
        self.size = [1] * n  # size[i] は i を根とするグループのサイズ

    def find(self, x):  # x の根を返す
        if self.parent[x] == x:
            return x
        else:
            self.parent[x] = self.find(self.parent[x])  # 経路圧縮
            return self.parent[x]

    def unite(self, x, y):  # x, y の属する集合を併合する
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                self.parent[x] = y
                self.size[y] += self.size[x]
            else:
                self.parent[y] = x
                self.size[x] += self.size[y]
                if self.rank[x] == self.rank[y]:
                    self.rank[x] += 1

    def is_same(self, x, y):  # x, y が同じ集合に属するか判定する
        return self.find(x) == self.find(y)

    def group_size(self, x):  # x が属する集合の大きさを返す
        return self.size[self.find(x)]

    def group_members(self, x):  # x が属する集合の要素を返す
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):  # すべての根をリストで返す
        return [i for i, x in enumerate(self.parent) if i == x]

    def group_count(self):  # 木の数を返す
        return len(self.roots())

    def all_group_members(self):  # すべての木の要素を辞書で返す
        return {r: self.group_members(r) for r in self.roots()}

#a = [i+1 for i in range(n)]
d = UnionFind(n)

for i in range(m):
    d.unite(L[i][0],L[i][1])

print(n-d.group_count())

Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)

Buggy python submission (verdict: Runtime Error):
n,m = map(int,input().split())
L = [list(map(int,input().split())) for i in range(m)]


class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parent = [i for i in range(n)]  # 親
        self.rank = [1] * n  # 木の高さ
        self.size = [1] * n  # size[i] は i を根とするグループのサイズ

    def find(self, x):  # x の根を返す
        if self.parent[x] == x:
            return x
        else:
            self.parent[x] = self.find(self.parent[x])  # 経路圧縮
            return self.parent[x]

    def unite(self, x, y):  # x, y の属する集合を併合する
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                self.parent[x] = y
                self.size[y] += self.size[x]
            else:
                self.parent[y] = x
                self.size[x] += self.size[y]
                if self.rank[x] == self.rank[y]:
                    self.rank[x] += 1

    def is_same(self, x, y):  # x, y が同じ集合に属するか判定する
        return self.find(x) == self.find(y)

    def group_size(self, x):  # x が属する集合の大きさを返す
        return self.size[self.find(x)]

    def group_members(self, x):  # x が属する集合の要素を返す
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):  # すべての根をリストで返す
        return [i for i, x in enumerate(self.parent) if i == x]

    def group_count(self):  # 木の数を返す
        return len(self.roots())

    def all_group_members(self):  # すべての木の要素を辞書で返す
        return {r: self.group_members(r) for r in self.roots()}

#a = [i+1 for i in range(n)]
d = UnionFind(n)

for i in range(m):
    d.unite(L[i][0],L[i][1])
ans = 10**32
for i in range(n):
    ans = min(ans,n-d.group_size(i))
print(ans)

Fixed submission:
n,m = map(int,input().split())

class Unionfind:
     
    def __init__(self,n):
        self.uf = [-1]*n
 
    def find(self,x):
        if self.uf[x] < 0:
            return x
        else:
            self.uf[x] = self.find(self.uf[x])
            return self.uf[x]
 
    def same(self,x,y):
        return self.find(x) == self.find(y)
 
    def union(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if self.uf[x] > self.uf[y]:
            x,y = y,x
        self.uf[x] += self.uf[y]
        self.uf[y] = x
        return True
 
    def size(self,x):
        x = self.find(x)
        return -self.uf[x]
#a = [i+1 for i in range(n)]
d = Unionfind(n)

for i in range(m):
    a,b = map(int,input().split())
    d.union(a-1,b-1)
    
L = []
for i in range(n):
    c = d.find(i)
    L.append(c)
#print(L)
print(len(set(L))-1)