Problem: There are N persons called Person 1 through Person N.  You are given M facts that "Person A_i and Person B_i are friends." The same fact may be given multiple times.  If X and Y are friends, and Y and Z are friends, then X and Z are also friends. There is no friendship that cannot be derived from the M given facts.  Takahashi the evil wants to divide the N persons into some number of groups so that every person has no friend in his/her group.  At least how many groups does he need to make?

Submission attempts (in order):
# D
from collections import Counter
n, m = map(int, input().split())
ab = [list(map(int, input().split()))for _ in range(m)]
ab.sort(key=lambda x:x[1])
ab.sort(key=lambda x:x[0])
# print(ab)
people=[0]*n
for i in ab:
    if people[i[0]-1]==0:
        people[i[0]-1]=i[0]
    if people[i[1]-1]==0:
        people[i[1]-1]=people[i[0]-1]
# print(people)
people=Counter(people).most_common()
print(people[0][1])

# D
from collections import Counter
n, m = map(int, input().split())
ab = [list(map(int, input().split()))for _ in range(m)]
for i in ab:
    if i[0] > i[1]:
        i[0], i[1] = i[1], i[0]
ab.sort(key=lambda x: x[1])
ab.sort(key=lambda x: x[0])
print(ab)
people = [0]*n
for i in ab:
    if people[i[0]-1] == 0:
        people[i[0]-1] = i[0]
    people[i[1]-1] = people[i[0]-1]
print(people)
# Counter.(list).most_common()
people = Counter(people).most_common()
print(people[0][1])


# D
from collections import Counter
n, m = map(int, input().split())
ab = [list(map(int, input().split()))for _ in range(m)]
for i in ab:
    if i[0]>i[1]:
        i[0],i[1]=i[1],i[0]
ab.sort(key=lambda x:x[1])
ab.sort(key=lambda x:x[0])
print(ab)
people=[0]*n
for i in ab:
    if people[i[0]-1]==0:
        people[i[0]-1]=i[0]
    if people[i[1]-1]==0:
        people[i[1]-1]=people[i[0]-1]
print(people)
people=Counter(people).most_common()
print(people[0][1])

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 relf.roots()}

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

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


for i in range(M):
    a,b=map(int,input().split())
    uf.union(a-1,b-1)

ans=0
roots=uf.roots()

for i in roots:
    ans=max(ans,uf.size(i))

print(ans)


Verdicts: Wrong Answer

Wrong Answer

Wrong Answer

Accepted