Problem:


Score : 400 points

Problem Statement

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?

Constraints

2 \leq N \leq 2\times 10^5

0 \leq M \leq 2\times 10^5

1\leq A_i,B_i\leq N

A_i \neq B_i

Input

Input is given from Standard Input in the following format:

N M
A_1 B_1
\vdots
A_M B_M

Output

Print the answer.

Sample Input 1

5 3
1 2
3 4
5 1

Sample Output 1

3

Dividing them into three groups such as \{1,3\}, \{2,4\}, and \{5\} achieves the goal.

Sample Input 2

4 10
1 2
2 1
1 2
2 1
1 2
1 3
1 4
2 3
2 4
3 4

Sample Output 2

4

Sample Input 3

10 4
3 1
4 1
5 9
2 6

Sample Output 3

3



Sample input:
5 3
1 2
3 4
5 1


Sample output:
3

Submission status: Accepted

Solution code:
def examA():
    D,T,S = LI()
    if (D-1)//S<T:
        ans = "Yes"
    else:
        ans = "No"
    print(ans)
    return

def examB():
    S = SI()
    T = SI()
    s = len(S)
    t = len(T)
    ans = t
    for i in range(s-t+1):
        cnt = 0
        for j in range(t):
            if S[i+j]!=T[j]:
                cnt += 1
        ans = min(ans,cnt)

    print(ans)
    return

def examC():
    N = I()
    A = LI()
    S = sum(A)
    cnt = 0
    for a in A:
        cnt += (S-a)*a
        cnt %= mod
    ans = cnt * pow(2,mod-2,mod) % mod
    print(ans)
    return

def examD():
    class UnionFind():
        def __init__(self, n):
            self.parent = [-1 for _ in range(n)]
            # 正==子: 根の頂点番号 / 負==根: 連結頂点数

        def reset(self):
            self.parent = [-1] * len(self.parent)

        def find(self, x):
            # 要素xが属するグループの根を返す
            if self.parent[x] < 0:
                return x
            else:
                self.parent[x] = self.find(self.parent[x])
                return self.parent[x]

        def unite(self, x, y):
            # 要素xが属するグループと要素yが属するグループとを併合する
            x, y = self.find(x), self.find(y)
            if x == y:
                return False
            else:
                if self.size(x) < self.size(y):
                    x, y = y, x
                self.parent[x] += self.parent[y]
                self.parent[y] = x

        def same(self, x, y):
            # 要素x, yが同じグループに属するかどうかを返す
            return self.find(x) == self.find(y)

        def size(self, x):
            # 要素xが属するグループのサイズ（要素数）を返す
            x = self.find(x)
            return -self.parent[x]

        def is_root(self, x):
            # 要素の根をリストで返す
            return self.parent[x] < 0

        def roots(self):
            # すべての根の要素をリストで返す
            return [i for i, x in enumerate(self.parent) if x < 0]

        def members(self, x):
            # 要素xが属するグループに属する要素をリストで返す
            root = self.find(x)
            return [i for i in range(self.n) if self.find(i) == root]

        def group_count(self):
            # グループの数を返す
            return len(self.roots())

        def all_group_members(self):
            # {ルート要素: [そのグループに含まれる要素のリスト], ...}の辞書を返す
            return {r: self.members(r) for r in self.roots()}
    N, M = LI()
    uf = UnionFind(N)
    for _ in range(M):
        a, b = LI()
        a -= 1; b -= 1
        uf.unite(a,b)
    cnt = 0
    for i in range(N):
        cnt = max(cnt,uf.size(i))

    ans = cnt
    print(ans)
    return

def examE():
    ans = 0
    print(ans)
    return

def examF():
    ans = 0
    print(ans)
    return

from decimal import getcontext,Decimal as dec
import sys,bisect,itertools,heapq,math,random
from copy import deepcopy
from heapq import heappop,heappush,heapify
from collections import Counter,defaultdict,deque
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
def I(): return int(input())
def LI(): return list(map(int,sys.stdin.readline().split()))
def DI(): return dec(input())
def LDI(): return list(map(dec,sys.stdin.readline().split()))
def LSI(): return list(map(str,sys.stdin.readline().split()))
def LS(): return sys.stdin.readline().split()
def SI(): return sys.stdin.readline().strip()
global mod,mod2,inf,alphabet,_ep
mod = 10**9 + 7
mod2 = 998244353
inf = 10**18
_ep = dec("0.000000000001")
alphabet = [chr(ord('a') + i) for i in range(26)]
alphabet_convert = {chr(ord('a') + i): i for i in range(26)}

getcontext().prec = 28

sys.setrecursionlimit(10**7)

if __name__ == '__main__':
    examD()

"""
142
12 9 1445 0 1
asd dfg hj o o
aidn
"""

Submission status: Accepted

Solution code:
from collections import defaultdict
class UnionFind:
    def __init__(self, num):
        self.table = [-1 for _ in range(num)]
        self.sz = defaultdict(lambda:1)

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

    def union(self, x, y):
        s1 = self.find(x)
        s2 = self.find(y)

        if s1 != s2:
            size = self.sz[s1]+self.sz[s2]
            if self.table[s1] <= self.table[s2]:
                self.table[s1] += self.table[s2]
                self.table[s2] = s1
            else:
                self.table[s2] += self.table[s1]
                self.table[s1] = s2
            s = self.find(x)
            self.sz[s] = size
            return True
        return False

    def size(self, x):
        s = self.find(x)
        return self.sz[s]

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

ans = 0
for i in range(N):
    ans = max(ans,u.size(i))

print(ans)

Submission status: Accepted

Solution code:
class DisjointSetUnion:
    def __init__(self, n):
        self.parent = list(range(n))
        self.size = [1] * n
        self.num_sets = n

    def find(self, a):
        acopy = a
        while a != self.parent[a]:
            a = self.parent[a]
        while acopy != a:
            self.parent[acopy], acopy = a, self.parent[acopy]
        return a

    def union(self, a, b):
        a, b = self.find(a), self.find(b)
        if a != b:
            if self.size[a] < self.size[b]:
                a, b = b, a

            self.num_sets -= 1
            self.parent[b] = a
            self.size[a] += self.size[b]

    def set_size(self, a):
        return self.size[self.find(a)]

    def __len__(self):
        return self.num_sets

N, M = map(int, input().split())
UF = DisjointSetUnion(N)
for _ in range(M):
    a, b = map(int, input().split())
    UF.union(a-1,b-1)

best = 0
for i in range(N):
    best = max(best,UF.set_size(i))
print(best)

Submission status: Accepted

Solution code:
def find(x):
    '''
    xの根を求める
    O(α(N))
    '''
    if par[x] < 0:
        return x
    else:
        par[x] = find(par[x])
        return par[x]


def union(x, y):
    '''
    xとyの属する集合を併合する
    '''
    x = find(x)
    y = find(y)
    
    if x == y:
        return False

    if par[x] > par[y]:
        x, y = y, x

    par[x] += par[y]
    par[y] = x
    return True


def size(x):
    '''
    xが属する集合の個数を求める
    '''
    return -par[find(x)]


def same(x, y):
    '''
    xとyが同じ集合に属するかを判定する
    '''
    return find(x) == find(y)


n, m = map(int, input().split())

par = [-1] * n
for _ in range(m):
    a, b = map(int, input().split())
    if not same(a-1, b-1):
        union(a-1, b-1)

res = 0
for i in range(n):
    res = max(res, size(i))

print(res)

Submission status: Accepted

Solution code:
class UnionFind():
    # 作りたい要素数nで初期化
    # 使用するインスタンス変数の初期化
    def __init__(self, n):
        self.n = n
        # root[x]<0ならそのノードが根かつその値が木の要素数
        # rootノードでその木の要素数を記録する
        self.root = [-1] * (n + 1)
        # 木をくっつける時にアンバランスにならないように調整する
        self.rnk = [0] * (n + 1)
    # ノードxのrootノードを見つける

    def Find_Root(self, x):
        if(self.root[x] < 0):
            return x
        else:
            # ここで代入しておくことで、後の繰り返しを避ける
            self.root[x] = self.Find_Root(self.root[x])
            return self.root[x]
    # 木の併合、入力は併合したい各ノード

    def Unite(self, x, y):
        # 入力ノードのrootノードを見つける
        x = self.Find_Root(x)
        y = self.Find_Root(y)
        # すでに同じ木に属していた場合
        if(x == y):
            return
        # 違う木に属していた場合rnkを見てくっつける方を決める
        elif(self.rnk[x] > self.rnk[y]):
            self.root[x] += self.root[y]
            self.root[y] = x
        else:
            self.root[y] += self.root[x]
            self.root[x] = y
            # rnkが同じ（深さに差がない場合）は1増やす
            if(self.rnk[x] == self.rnk[y]):
                self.rnk[y] += 1
    # xとyが同じグループに属するか判断

    def isSameGroup(self, x, y):
        return self.Find_Root(x) == self.Find_Root(y)
    # ノードxが属する木のサイズを返す

    def Count(self, x):
        return -self.root[self.Find_Root(x)]


import sys
sys.setrecursionlimit(10000000)
input = sys.stdin.readline
n, m = map(int, input().split())
u = UnionFind(n)
for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    u.Unite(a, b)
print(max(u.Count(i) for i in range(n)))

Submission status: Accepted

Solution code:
from collections import defaultdict, deque, Counter
from heapq import heappush, heappop, heapify
import math
import bisect
import random
from itertools import permutations, accumulate, combinations, product
import sys
import string
from bisect import bisect_left, bisect_right
from math import factorial, ceil, floor
from operator import mul
from functools import reduce


sys.setrecursionlimit(2147483647)
INF = 10 ** 13
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return sys.stdin.readline().rstrip().split()
def S(): return sys.stdin.readline().rstrip()
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
def SRL(n): return [list(S()) for i in range(n)]
def MSRL(n): return [[int(j) for j in list(S())] for i in range(n)]

mod=10**9+7


class UnionFind:
    def __init__(self, n):
        # 負  : 根であることを示す。絶対値はランクを示す
        # 非負: 根でないことを示す。値は親を示す
        self.table = [-1] * n
        self.size = [1] * n
        # self.group_num = n

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

    def get_size(self, x):
        r = self.root(x)
        return self.size[r]

    def is_same(self, x, y):
        return self.root(x) == self.root(y)

    def union(self, x, y):
        r1 = self.root(x)
        r2 = self.root(y)
        if r1 == r2:
            return
        # ランクの取得
        d1 = self.table[r1]
        d2 = self.table[r2]
        if d1 <= d2:
            self.table[r2] = r1
            self.size[r1] += self.size[r2]
            if d1 == d2:
                self.table[r1] -= 1
        else:
            self.table[r1] = r2
            self.size[r2] += self.size[r1]
        # self.group_num -= 1


n,m=LI()
U=UnionFind(n)
for _ in range(m):
    a,b=LI()
    U.union(a-1,b-1)

ans=0
for i in range(n):
    ans=max(ans, U.get_size(i))

print(ans)

Submission status: Accepted

Solution code:
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())

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

    def get_all_members(self):
        pare_d = {}
        for i in range(self.n):
            parent = self.find(i)
            pare_d.setdefault(parent,[])
            pare_d[parent].append(i)
        return list(pare_d.values())

    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 _ in range(m):
    a,b = map(int, input().split())
    uf.union(a-1,b-1)

all_g = uf.get_all_members()
max_len = 0
for g in all_g:
    max_len = max(max_len, len(g))

print(max_len)

Submission status: Accepted

Solution code:
class UnionFind():
    def __init__(self, n):
        self.par = [-1] * n

    def root(self, x):
        if self.par[x] < 0:
            return x
        else:
            self.par[x] = self.root(self.par[x])  # contraction
            return self.par[x]

    def unite(self, x, y):
        x, y = self.root(x), self.root(y)
        if x != y:
            if self.par[x] > self.par[y]:  # merge technique
                x, y = y, x
            self.par[x] += self.par[y]
            self.par[y] = x

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

    def size(self, x):
        return -self.par[self.root(x)]


n, m = map(int, input().split())
uf = UnionFind(n)
for _ in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    uf.unite(a, b)

ans = max(uf.size(i) for i in range(n))
print(ans)

Submission status: Accepted

Solution code:
#UnionFind
import sys
sys.setrecursionlimit(10**9)
class UnionFind:
  def __init__(self, n):
    self.n = [-1]*n
    self.r = [0]*n
    self.siz = n

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

  def unite(self, x, y):
    x = self.find_root(x)
    y = self.find_root(y)
    if x == y:
      return
    elif self.r[x] > self.r[y]:
      self.n[x] += self.n[y]
      self.n[y] = x
    else:
      self.n[y] += self.n[x]
      self.n[x] = y
      if self.r[x] == self.r[y]:
        self.r[y] += 1
    self.siz -= 1

  def root_same(self, x, y):
    return self.find_root(x) == self.find_root(y)

  def count(self, x):
    return -self.n[self.find_root(x)]

  def size(self):
    return self.siz

n,m=map(int,input().split())
u=UnionFind(n)
for _ in range(m):
  a,b=map(int,input().split())
  a-=1
  b-=1
  u.unite(a,b)
ans=0
for i in range(n):
  ans=max(ans,u.count(i))
print(ans)

Submission status: Accepted

Solution code:
def find(x):
    if par[x] < 0:
        return x
    else:
        par[x] = find(par[x])
        return par[x]
# 同一の集合の判定
def same(x, y):
    if find(x) == find(y):
        return True
    else:
        return False
# 集合の併合
def unite(x, y):
    x = find(x)
    y = find(y)
    if x == y:
        return
    if par[x] > par[y]:
        x, y = y, x
    par[x] += par[y]
    par[y] = x

# 集合の数
def uCnt(x):
    return -par[find(x)]

N, M = map(int, input().split())
par = [-1 for i in range(N)]

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

ans = min(par)
print(-ans)

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline
from collections import *

class Unionfind:
    def __init__(self, n):
        self.par = [-1]*n
        self.rank = [1]*n
    
    def root(self, x):
        r = x
        
        while not self.par[r]<0:
            r = self.par[r]
        
        t = x
        
        while t!=r:
            tmp = t
            t = self.par[t]
            self.par[tmp] = r
        
        return r
    
    def unite(self, x, y):
        rx = self.root(x)
        ry = self.root(y)
        
        if rx==ry:
            return
        
        if self.rank[rx]<=self.rank[ry]:
            self.par[ry] += self.par[rx]
            self.par[rx] = ry
            
            if self.rank[rx]==self.rank[ry]:
                self.rank[ry] += 1
        else:
            self.par[rx] += self.par[ry]
            self.par[ry] = rx
    
    def is_same(self, x, y):
        return self.root(x)==self.root(y)
    
    def count(self, x):
        return -self.par[self.root(x)]

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

for _ in range(M):
    A, B = map(int, input().split())
    uf.unite(A-1, B-1)

ans = 0
r = set()

for i in range(N):
    r.add(uf.root(i))
    
for ri in r:
    ans = max(ans, uf.count(ri))

print(ans)

Submission status: Accepted

Solution code:
import os,io
input=io.BytesIO(os.read(0,os.fstat(0).st_size)).readline
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=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
for i in range(n):
  ans=max(ans,uf.size(i))
print(ans)

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline

class UnionFind:
    def __init__(self, n):
        self.n = n
        self.par = [-1]*(n+1)#それぞれの要素がどの要素の子であるか

    def find(self, x):
        if self.par[x] < 0:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]#それぞれの要素の根を再帰的に求める

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.par[x] > self.par[y]:
            x, y = y, x
        
        self.par[x] += self.par[y]
        self.par[y] = x

    def same(self, x, y):
        return self.find(x) == self.find(y)#x,yが同じ集合に属するかどうか
    
    def size(self, x):
        return -self.par[self.find(x)]
    
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if root == self.find(i)]        

def main():
    n, m = map(int, input().split())
    
    union = UnionFind(n)
    
    for i in range(m):
        x, y = map(int, input().split())
        union.union(x, y)
    
    ans = -min(union.par)
    print(ans)
    
    
    
    
if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
class UnionFind:
    def __init__(self, N):
        self.p = list(range(N))
        self.rank = [0] * N
        self.size = [1] * N

    def root(self, x):
        if self.p[x] != x:
            self.p[x] = self.root(self.p[x])
        return self.p[x]

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

    def unite(self, x, y):
        u = self.root(x)
        v = self.root(y)
        if u == v:
            return
        if self.rank[u] < self.rank[v]:
            self.p[u] = v
            self.size[v] += self.size[u]
            self.size[u] = 0
        else:
            self.p[v] = u
            self.size[u] += self.size[v]
            self.size[v] = 0
            if self.rank[u] == self.rank[v]:
                self.rank[u] += 1

    def count(self, x):
        return self.size[self.root(x)]

N, M = map(int, input().split())
uf = UnionFind(N+1)
for _ in range(M):
    a, b = map(int, input().split())
    uf.unite(a, b)
ans = max(uf.count(i) for i in range(1, N+1))
print(ans)

Submission status: Accepted

Solution code:

def uf_find(n,p):

    ufl = []

    while p[n] != n:
        ufl.append(n)
        n = p[n]

    for i in ufl:
        p[i] = n

    return n


def uf_union(a,b,p,rank,s):

    ap = uf_find(a,p)
    bp = uf_find(b,p)

    if ap == bp:
        return True
    else:

        if rank[ap] > rank[bp]:
            p[bp] = ap
            s[ap] += s[bp]
        elif rank[ap] < rank[bp]:
            p[ap] = bp
            s[bp] += s[ap]
        else:
            p[bp] = ap
            s[ap] += s[bp]
            rank[ap] += 1

        return False

from sys import stdin
N,M = map(int,stdin.readline().split())

p = [i for i in range(N)]
rank = [0] * N
s = [1] * N

for i in range(M):

    A,B = map(int,stdin.readline().split())
    A -= 1
    B -= 1
    uf_union(A,B,p,rank,s)

print (max(s))

Submission status: Accepted

Solution code:

class UnionFind:
    def __init__(self, n):
        self.par = list(range(n))
        self.rank = [0] * n
        self.size = [1] * n

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

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

        if x == y:
            return

        if self.rank[x] == self.rank[y]:
            self.rank[x] += 1
        elif self.rank[x] < self.rank[y]:
            x, y = y, x

        self.par[y] = x
        self.size[x] += self.size[y]

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

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


N, M = map(int, input().split())
X = [list(map(int, input().split())) for _ in range(M)]

tree = UnionFind(N + 1)
for a, b in X:
    tree.unite(a, b)

res = max(tree.get_size(n) for n in range(1, N + 1))
print(res)

Submission status: Accepted

Solution code:
class UnionFind():
    # 作りたい要素数nで初期化
    def __init__(self, n):
        self.n = n
        self.root = [-1]*(n+1)
        self.rnk = [0]*(n+1)

    # ノードxのrootノードを見つける
    def Find_Root(self, x):
        if(self.root[x] < 0):
            return x
        else:
            self.root[x] = self.Find_Root(self.root[x])
            return self.root[x]
    
    # 木の併合、入力は併合したい各ノード
    def Unite(self, x, y):
        x = self.Find_Root(x)
        y = self.Find_Root(y)
        if(x == y):
            return 
        elif(self.rnk[x] > self.rnk[y]):
            self.root[x] += self.root[y]
            self.root[y] = x

        else:
            self.root[y] += self.root[x]
            self.root[x] = y
            if(self.rnk[x] == self.rnk[y]):
                self.rnk[y] += 1
    
    def isSameGroup(self, x, y):
        return self.Find_Root(x) == self.Find_Root(y)

    # ノードxが属する木のサイズ
    def Count(self, x):
        return -self.root[self.Find_Root(x)]


N, M = map(int, input().split())
uni = UnionFind(N)
for _ in range(M):
    a, b = map(int, input().split())
    uni.Unite(a-1, b-1)

ans = 0
for i in range(N):
    ans = max(ans, uni.Count(i))
print(ans)

Submission status: Accepted

Solution code:
import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
sys.setrecursionlimit(10 ** 9)
INF = 1 << 60
MOD = 1000000007


class UnionFind:
    # Reference: https://note.nkmk.me/python-union-find/
    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 same(self, x, y):
        return self.find(x) == self.find(y)

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


def main():
    N, M, *AB = map(int, read().split())

    uf = UnionFind(N)
    for a, b in zip(*[iter(AB)] * 2):
        uf.union(a - 1, b - 1)

    ans = 0
    for i in range(N):
        if ans < uf.size(i):
            ans = uf.size(i)

    print(ans)
    return


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
import sys
sys.setrecursionlimit(10**7) #再帰関数の上限,10**5以上の場合python
import math
from copy import copy, deepcopy
from copy import deepcopy as dcp
from operator import itemgetter
from bisect import bisect_left, bisect, bisect_right#2分探索
#bisect_left(l,x), bisect(l,x)#aはソート済みである必要あり。aの中からx未満の要素数を返す。rightだと以下
from collections import deque, defaultdict
#deque(l), pop(), append(x), popleft(), appendleft(x)
#q.rotate(n)で → にn回ローテート
from collections import Counter#文字列を個数カウント辞書に、
#S=Counter(l),S.most_common(x),S.keys(),S.values(),S.items()
from itertools import accumulate,combinations,permutations,product#累積和
#list(accumulate(l))
from heapq import heapify,heappop,heappush
#heapify(q),heappush(q,a),heappop(q) #q=heapify(q)としないこと、返り値はNone
from functools import reduce,lru_cache#pypyでもうごく
#@lru_cache(maxsize = None)#maxsizeは保存するデータ数の最大値、2**nが最も高効率
from decimal import Decimal
from argparse import ArgumentParser

args=ArgumentParser()
args.add_argument('-loc', '--local', type=bool,default=False)
LOCAL=args.parse_args().local

def input(): 
    x=sys.stdin.readline(); 
    if x[-1]=="\n": 
        return x.rstrip() 
    return x
    
def printe(*x):_=print("## ",*x,file=sys.stderr) if LOCAL else 0
def printl(li): _=print(*li, sep="\n") if li else None
def argsort(s, return_sorted=False): 
    inds=sorted(range(len(s)), key=lambda k: s[k])
    if return_sorted: return inds, [s[i] for i in inds]
    return inds
def alp2num(c,cap=False): return ord(c)-97 if not cap else ord(c)-65
def num2alp(i,cap=False): return chr(i+97) if not cap else chr(i+65)
def matmat(A,B):
    K,N,M=len(B),len(A),len(B[0])
    return [[sum([(A[i][k]*B[k][j]) for k in range(K)]) for j in range(M)] for i in range(N)]
def matvec(M,v):
    N,size=len(v),len(M)
    return [sum([M[i][j]*v[j] for j in range(N)]) for i in range(size)]
def T(M):
    n,m=len(M),len(M[0])
    return [[M[j][i] for j in range(n)] for i in range(m)]
def binr(x): return bin(x)[2:]
def bitcount(x): #xは64bit整数
    x= x - ((x >> 1) & 0x5555555555555555)
    x= (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333)
    x= (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f 
    x+= (x >> 8); x+= (x >> 16); x+= (x >> 32) 
    return x & 0x7f

class unionfind:#早いunionfind,class[i]のように要素指定すると親を得ることができる
    def __init__(self, elements=None):#elementsで初期化
        if elements is None:
            elements = ()
        self.parents = {}
        self.weights = {}
        for x in elements:
            self.weights[x] = 1
            self.parents[x] = x

    def __getitem__(self, i):
        # check for previously unknown i
        if i not in self.parents:
            self.parents[i] = i
            self.weights[i] = 1
            return i
        path = [i]
        root = self.parents[i]
        while root != path[-1]:
            path.append(root)
            root = self.parents[root]
        for ancestor in path:#縮約
            self.parents[ancestor] = root
        return root

    def __iter__(self):#for parent in Class:
        return iter(self.parents)

    def union(self, *objects):#オブジェクトをすべて結合
        roots = [self[x] for x in objects]
        heaviest = max(roots, key=lambda r: self.weights[r])
        for r in roots:
            if r != heaviest:
                self.weights[heaviest] += self.weights[r]
                self.parents[r] = heaviest

    def __len__(self):
        return len(self.parents)

def main():
    mod = 1000000007
    #w.sort(key=itemgetter(1),reverse=True)  #二個目の要素で降順並び替え

    #N = int(input())
    N, M = map(int, input().split())
    #A = tuple(map(int, input().split())) #1行ベクトル
    #L = tuple(int(input()) for i in range(N)) #改行ベクトル
    #S = tuple(tuple(map(int, input().split())) for i in range(N)) #改行行列
    uf=unionfind(range(N))
    for i in range(M):
        a,b=map(int, input().split())
        a-=1;b-=1
        uf.union(a,b)
    ans=0
    for i in range(N):
        ans=max(ans,uf.weights[uf[i]])
    print(ans)



if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
n, m = map(int, input().split())

class UnionFind(object):
    def __init__(self, n):
        self._par = list(range(n))
        self.size = [1] * n
 
    def root(self, v):
        if self._par[v] == v:
            return v
        self._par[v] = self.root(self._par[v])
        return self._par[v]
 
    def unite(self, u, v):
        u, v = self.root(u), self.root(v)
        if u == v:
            return False
        if self.size[u] > self.size[v]:
            u, v = v, u # size[u] <= size[v]
        self.size[v] += self.size[u]
        self._par[u] = v
 
    def same(self, u, v):
        return self.root(u) == self.root(v)

uf = UnionFind(n)
for _ in range(m):
    a, b = map(int, input().split())
    uf.unite(a-1, b-1)

ans = 0
for i in range(n):
    ans = max(ans, uf.size[uf.root(i)])

print(ans)

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
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())
    
a=UnionFind(n)
for i in range(m):
    x,y=map(int,input().split())
    a.union(x-1,y-1)
ans=0
for i in range(n):
    ans=max(ans,a.size(i))
print(ans)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())

parent = [i + 1 for i in range(n)]
rank = [0 for i in range(n)]
size = [1 for i in range(n)]

def find(x):
    if parent[x - 1] == x:
        return x
    else:
        parent[x - 1] = find(parent[x - 1])
        return parent[x - 1]

def unite(x, y):
    x = find(x)
    y = find(y)
    if x == y:
        return
    if rank[x - 1] < rank[y - 1]:
        parent[x - 1] = y
        size[y - 1] += size[x - 1]
    else:
        parent[y - 1] = x
        size[x - 1] += size[y - 1]
        if rank[x - 1] == rank[y - 1]:
            rank[x - 1] += 1

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