Problem:


Score : 100 points

Problem Statement

You are given a directed graph with N vertices and M edges, not necessarily simple. The i-th edge is oriented from the vertex a_i to the vertex b_i.
Divide this graph into strongly connected components and print them in their topological order.

Constraints

1 \leq N \leq 500,000

1 \leq M \leq 500,000

0 \leq a_i, b_i < N

Input

Input is given from Standard Input in the following format:

N M
a_0 b_0
a_1 b_1
:
a_{M - 1} b_{M - 1}

Output

Print 1+K lines, where K is the number of strongly connected components.
Print K on the first line. 
Print the information of each strongly connected component in next K lines in the following format, where l is the number of vertices in the strongly connected component and v_i is the index of the vertex in it.

l v_0 v_1 ... v_{l-1}

Here, for each edge (a_i, b_i), b_i should not appear in earlier line than a_i.

If there are multiple correct output, print any of them.

Sample Input 1

6 7
1 4
5 2
3 0
5 5
4 1
0 3
4 2

Sample Output 1

4
1 5
2 4 1
1 2
2 3 0



Sample input:
6 7
1 4
5 2
3 0
5 5
4 1
0 3
4 2


Sample output:
4
1 5
2 4 1
1 2
2 3 0

Submission status: Time Limit Exceeded

Solution code:
class Digraph:
    """重み[なし]有向グラフを生成する.

    """

    #入力定義
    def __init__(self,vertex=[]):
        self.vertex=set(vertex)

        self.edge_number=0
        self.vertex_number=len(vertex)

        self.adjacent_out={v:set() for v in vertex} #出近傍(vが始点)
        self.adjacent_in={v:set() for v in vertex} #入近傍(vが終点)

    #頂点の追加
    def add_vertex(self,*adder):
        for v in adder:
            if v not in self.vertex:
                self.adjacent_in[v]=set()
                self.adjacent_out[v]=set()

                self.vertex_number+=1
                self.vertex.add(v)

    #辺の追加
    def add_edge(self,From,To):
        for v in [From,To]:
            if v not in self.vertex:
                self.add_vertex(v)

        if To not in self.adjacent_in[From]:
            self.edge_number+=1

        self.adjacent_out[From].add(To)
        self.adjacent_in[To].add(From)

    #辺を除く
    def remove_edge(self,From,To):
        for v in [From,To]:
            if v not in self.vertex:
                self.add_vertex(v)

        if To in self.adjacent_out[From]:
            self.adjacent_out[From].remove(To)
            self.adjacent_in[To].remove(From)
            self.edge_number-=1

    #頂点を除く
    def remove_vertex(self,*vertexes):
        for  v in vertexes:
            if v in self.vertex:
                self.vertex_number-=1

                for u in self.adjacent_out[v]:
                    self.adjacent_in[u].remove(v)
                    self.edge_number-=1
                del self.adjacent_out[v]

                for u in self.adjacent_in[v]:
                    self.adjacent_out[u].remove(v)
                    self.edge_number-=1
                del self.adjacent_in[v]

    #Walkの追加
    def add_walk(self,*walk):
        N=len(walk)
        for k in range(N-1):
            self.add_edge(walk[k],walk[k+1])

    #Cycleの追加
    def add_cycle(self,*cycle):
        self.add_walk(*cycle)
        self.add_edge(cycle[-1],cycle[0])

    #頂点の交換
    def __vertex_swap(self,p,q):
        self.vertex.sort()

    #グラフに頂点が存在するか否か
    def vertex_exist(self,v):
        return v in self.vertex

    #グラフに辺が存在するか否か
    def edge_exist(self,From,To):
        if not(self.vertex_exist(From) and self.vertex_exist(To)):
            return False
        return To in self.adjacent_out[From]

    #近傍
    def neighbohood(self,v):
        if not self.vertex_exist(v):
            return []
        return list(self.adjacent[v])

    #出次数
    def out_degree(self,v):
        if not self.vertex_exist(v):
            return 0

        return len(self.adjacent_out[v])

    #入次数
    def in_degree(self,v):
        if not self.vertex_exist(v):
            return 0

        return len(self.adjacent_in[v])

    #次数
    def degree(self,v):
        if not self.vertex_exist(v):
            return 0

        return self.out_degree(v)-self.in_degree(v)

    #頂点数
    def vertex_count(self):
        return len(self.vertex)

    #辺数
    def edge_count(self):
        return self.edge_number

    #頂点vを含む連結成分
    def connected_component(self,v):
        pass

#Topologycal Sort
def Topological_Sort(D):
    from collections import deque

    X={v:D.in_degree(v) for v in D.vertex}
    Q=deque([v for v in D.vertex if X[v]==0])

    S=[]
    while Q:
        u=Q.pop()
        S.append(u)
        for v in D.adjacent_out[u]:
            X[v]-=1
            if X[v]==0:
                Q.append(v)

    return S

#強連結成分に分解
def Strongly_Connected_Component_Decomposition(D,Mode=0):
    """有向グラフDを強連結成分に分解

    Mode:
    0(Defalt)---各強連結成分の頂点のリスト\n
    1        ---各頂点が属している強連結成分の番号\n
    2        ---0,1の両方\n
    """
    import sys
    from collections import deque

    T={x:-1 for x in D.vertex}
    Q=deque([])

    def f(v):
        T[v]=0
        for w in D.adjacent_out[v]:
            if T[w]==-1:
                f(w)

        Q.append(v)
        T[v]=len(Q)
    x=D.vertex.pop()
    D.vertex.add(x)

    RT=sys.getrecursionlimit()
    sys.setrecursionlimit(5*10**5)
    for v in D.vertex:
        if T[v]==-1:
            f(v)
    sys.setrecursionlimit(RT)

    T={x:-1 for x in D.vertex}
    C=[]
    p=0

    for v in Q:
        if T[v]==-1:
            T[v]=p
            P=[v]
            R=deque([v])

            while R:
                u=R.popleft()
                for w in D.adjacent_out[u]:
                    if T[w]==-1:
                        T[w]=p
                        R.append(w)
                        P.append(w)
            C.append(P)
            p+=1

    if Mode==1:
        return T
    elif Mode==2:
        return (C,T)
    else:
        return C

#Cycleを縮約
def Cycle_Reduction(D):
    B,C=Strongly_Connected_Component_Decomposition(D,2)

    R=[K[0] for K in B]

    E=Digraph(R)
    for a in D.vertex:
        for b in D.adjacent_out[a]:
            if C[a]!=C[b]:
                E.add_edge(R[C[a]],R[C[b]])
    return E
#================================================
N,M=map(int,input().split())
D=Digraph(list(range(N)))

for _ in range(M):
    a,b=map(int,input().split())
    D.add_edge(a,b)

(B,C)=Strongly_Connected_Component_Decomposition(D,2)
E=Cycle_Reduction(D)
T=Topological_Sort(E)

print(len(T))
for c in T:
    L=B[C[c]]
    print(len(L)," ".join(map(str,L)))

Submission status: Time Limit Exceeded

Solution code:
from networkx import*
N,M,*T=map(int,open(0).read().split())
G=DiGraph()
G.add_nodes_from(range(N))
G.add_edges_from(zip(T[::2],T[1::2]))
*t,=strongly_connected_components(G)
print(len(t))
for s in t[::-1]:print(len(s),*s)

Submission status: Time Limit Exceeded

Solution code:
import sys
input = lambda : sys.stdin.readline().rstrip()
sys.setrecursionlimit(max(1000, 10**9))
write = lambda x: sys.stdout.write(x+"\n")


n,m = map(int, input().split())
import networkx as nx
g = nx.DiGraph()
for i in range(n):
    g.add_node(i)
for _ in range(m):
    u,v = map(int, input().split())
    g.add_edge(u,v)
comp = list(nx.strongly_connected_components(g))
print(len(comp))
for item in reversed(comp):
    print(len(item), " ".join(map(str, item)))

Submission status: Time Limit Exceeded

Solution code:
import sys
input = lambda : sys.stdin.readline().rstrip()
sys.setrecursionlimit(max(1000, 10**9))
write = lambda x: sys.stdout.write(x+"\n")


n,m = map(int, input().split())
ns = [[] for _ in range(n)]
for _ in range(m):
    u,v = map(int, input().split())
    ns[u].append(v)
import networkx as nx
g = nx.DiGraph()
for i in range(n):
    g.add_node(i)
for i in range(n):
    for j in ns[i]:
        g.add_edge(i,j)
comp = list(nx.strongly_connected_components(g))
print(len(comp))
for item in comp[::-1]:
    print(len(item), " ".join(map(str, item)))

Submission status: Memory Limit Exceeded

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

sys.setrecursionlimit(10**6 + 5)

def dfs_numbering(i, M, V, ANS, cnt, v):
    V[i] = v
    for x in M[i]:
        if V[x] == -1:
            cnt = dfs_numbering(x, M, V, ANS, cnt, v)
    ANS[i] = cnt
    return cnt + 1

class scc():
    def __init__(self, n):
        self.n = n
        self.M = [[] for i in range(n)]
        self.IM = [[] for i in range(n)]

    def add_edge(self, frm, to):
        self.M[frm].append(to)
        self.IM[to].append(frm)

    def scc_list(self):
        n = self.n
        V = [-1] * n
        ANS = [-1] * n

        cnt = 0
        for i in range(n):
            if V[i] == -1:
                cnt = dfs_numbering(i, self.M, V, ANS, cnt, 0)

        # print(ANS)

        ANS1 = [[ANS[i], i] for i in range(n)]
        ANS1.sort(reverse=True)

        # print(ANS1)

        V = [-1] * n
        ANS = [-1] * n
        v = 0
        for i in range(n):
            if V[ANS1[i][1]] == -1:
                dfs_numbering(ANS1[i][1], self.IM, V, ANS, 0, v)
                v += 1

        FANS = [[] for i in range(v)]
        for i in range(n):
            FANS[V[i]].append(i)

        return FANS

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

S = scc(n)
for i in range(m):
    frm, to = map(int,input().split())
    S.add_edge(frm, to)
ANS = S.scc_list()

print(len(ANS))
for i in range(len(ANS)):
    print(len(ANS[i]), end=" ")
    print(*ANS[i])

Submission status: Memory Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline
n, m = map(int,input().split())
C = [list(map(int,input().split())) for i in range(m)]

sys.setrecursionlimit(m+5)

def dfs_numbering(i, M, V, ANS, cnt, v):
    V[i] = v
    for x in M[i]:
        if V[x] == -1:
            cnt = dfs_numbering(x, M, V, ANS, cnt, v)
    ANS[i] = cnt
    return cnt + 1

class scc():
    def __init__(self, n):
        self.n = n
        self.M = [[] for i in range(n)]
        self.IM = [[] for i in range(n)]

    def add_edge(self, frm, to):
        self.M[frm].append(to)
        self.IM[to].append(frm)

    def scc_list(self):
        n = self.n
        V = [-1] * n
        ANS = [-1] * n

        cnt = 0
        for i in range(n):
            if V[i] == -1:
                cnt = dfs_numbering(i, self.M, V, ANS, cnt, 0)

        # print(ANS)

        ANS1 = [[ANS[i], i] for i in range(n)]
        ANS1.sort(reverse=True)

        # print(ANS1)

        V = [-1] * n
        ANS = [-1] * n
        v = 0
        for i in range(n):
            if V[ANS1[i][1]] == -1:
                dfs_numbering(ANS1[i][1], self.IM, V, ANS, 0, v)
                v += 1

        FANS = [[] for i in range(v)]
        for i in range(n):
            FANS[V[i]].append(i)

        return FANS

S = scc(n)
for i in range(m):
    S.add_edge(C[i][0], C[i][1])
ANS = S.scc_list()

print(len(ANS))
for i in range(len(ANS)):
    print(*([len(ANS[i])] + ANS[i]))

Submission status: Memory Limit Exceeded

Solution code:
import sys
input = sys.stdin.readline
n, m = map(int,input().split())
C = [list(map(int,input().split())) for i in range(m)]

sys.setrecursionlimit(10**6 + 5)

def dfs_numbering(i, M, V, ANS, cnt, v):
    V[i] = v
    for x in M[i]:
        if V[x] == -1:
            cnt = dfs_numbering(x, M, V, ANS, cnt, v)
    ANS[i] = cnt
    return cnt + 1

class scc():
    def __init__(self, n):
        self.n = n
        self.M = [[] for i in range(n)]
        self.IM = [[] for i in range(n)]

    def add_edge(self, frm, to):
        self.M[frm].append(to)
        self.IM[to].append(frm)

    def scc_list(self):
        n = self.n
        V = [-1] * n
        ANS = [-1] * n

        cnt = 0
        for i in range(n):
            if V[i] == -1:
                cnt = dfs_numbering(i, self.M, V, ANS, cnt, 0)

        # print(ANS)

        ANS1 = [[ANS[i], i] for i in range(n)]
        ANS1.sort(reverse=True)

        # print(ANS1)

        V = [-1] * n
        ANS = [-1] * n
        v = 0
        for i in range(n):
            if V[ANS1[i][1]] == -1:
                dfs_numbering(ANS1[i][1], self.IM, V, ANS, 0, v)
                v += 1

        FANS = [[] for i in range(v)]
        for i in range(n):
            FANS[V[i]].append(i)

        return FANS

S = scc(n)
for i in range(m):
    S.add_edge(C[i][0], C[i][1])
ANS = S.scc_list()

print(len(ANS))
for i in range(len(ANS)):
    print(*([len(ANS[i])] + ANS[i]))

Submission status: Accepted

Solution code:
class csr:
    def __init__(self,N,edges):
        self.start = [0]*(N+1)
        self.elist = [0]*len(edges)
        for e in edges:
            self.start[e[0]+1] += 1
        for i in range(1,N+1):
            self.start[i] += self.start[i-1] 
        counter = self.start[:]
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class scc_graph:
    #__slots__ = ['N','edges']
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        g = csr(N,self.edges)
        now_ord = group_num = 0
        visited = []
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = []
        for i in range(N):
            if order[i] == -1:
                stack.append(i);stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for j in range(g.start[v],g.start[v+1]):
                            to = g.elist[j]
                            if order[to] == -1:
                                stack.append(to);stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))

Submission status: Accepted

Solution code:
class csr:
    def __init__(self,N,edges):
        self.start = [0]*(N+1)
        self.elist = [0]*len(edges)
        for e in edges:
            self.start[e[0]+1] += 1
        for i in range(1,N+1):
            self.start[i] += self.start[i-1] 
        counter = self.start[:]
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class scc_graph:
    __slots__ = ['N','edges']
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        g = csr(N,self.edges)
        now_ord = group_num = 0
        visited = []
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = []
        for i in range(N):
            if order[i] == -1:
                stack.append(i);stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for j in range(g.start[v],g.start[v+1]):
                            to = g.elist[j]
                            if order[to] == -1:
                                stack.append(to);stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))

Submission status: Accepted

Solution code:
class scc_graph:
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        edges = self.edges
        start = [0]*(N+1)
        elist = [0]*len(edges)
        for e in edges:
            start[e[0]+1] += 1
        for i in range(1,N+1):
            start[i] += start[i-1] 
        counter = start[:]
        for e in edges:
            elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1        
        now_ord = group_num = 0
        visited = []
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = []
        for i in range(N):
            if order[i] == -1:
                stack.append(i)
                stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for i in range(start[v],start[v+1]):
                            to = elist[i]
                            if order[to] == -1:
                                stack.append(to)
                                stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))

Submission status: Accepted

Solution code:
class csr:
    def __init__(self,N,edges):
        self.start = [0]*(N+1)
        self.elist = [0]*len(edges)
        for e in edges:
            self.start[e[0]+1] += 1
        for i in range(1,N+1):
            self.start[i] += self.start[i-1] 
        counter = self.start[:]
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class scc_graph:
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        edges = self.edges
        start = [0]*(N+1)
        elist = [0]*len(edges)
        for e in edges:
            start[e[0]+1] += 1
        for i in range(1,N+1):
            start[i] += start[i-1] 
        counter = start[:]
        for e in edges:
            elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1        
        now_ord = group_num = 0
        visited = []
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = []
        for i in range(N):
            if order[i] == -1:
                stack.append(i)
                stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for i in range(start[v],start[v+1]):
                            to = elist[i]
                            if order[to] == -1:
                                stack.append(to)
                                stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))

Submission status: Accepted

Solution code:
class csr:
    def __init__(self,N,edges):
        self.start = [0]*(N+1)
        self.elist = [0]*len(edges)
        for e in edges:
            self.start[e[0]+1] += 1
        for i in range(1,N+1):
            self.start[i] += self.start[i-1] 
        counter = self.start[:]
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class scc_graph:
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        g = csr(N,self.edges)
        now_ord = group_num = 0
        visited = []
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = []
        for i in range(N):
            if order[i] == -1:
                stack.append(i)
                stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for i in range(g.start[v],g.start[v+1]):
                            to = g.elist[i]
                            if order[to] == -1:
                                stack.append(to)
                                stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))

Submission status: Accepted

Solution code:
from collections import deque
class csr:
    def __init__(self,N,edges):
        self.start = [0]*(N+1)
        self.elist = [0]*len(edges)
        for e in edges:
            self.start[e[0]+1] += 1
        for i in range(1,N+1):
            self.start[i] += self.start[i-1] 
        counter = self.start[:]
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class scc_graph:
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        g = csr(N,self.edges)
        now_ord = group_num = 0
        visited = deque()
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = deque()
        for i in range(N):
            if order[i] == -1:
                stack.append(i)
                stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for i in range(g.start[v],g.start[v+1]):
                            to = g.elist[i]
                            if order[to] == -1:
                                stack.append(to)
                                stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))

Submission status: Accepted

Solution code:
from collections import deque
class csr:
    def __init__(self,N,edges):
        self.start = [0]*(N+1)
        self.elist = [0]*len(edges)
        for e in edges:
            self.start[e[0]+1] += 1
        for i in range(1,N+1):
            self.start[i] += self.start[i-1] 
        counter = self.start[:]
        for e in edges:
            self.elist[counter[e[0]]] = e[1]
            counter[e[0]] += 1

class scc_graph:
    def __init__(self,N):
        self.N = N
        self.edges = []
    
    def add_edge(self,v,w):
        self.edges.append((v,w))

    def scc_ids(self):
        N = self.N
        g = csr(self.N,self.edges)
        now_ord = group_num = 0
        visited = deque()
        low = [0]*N
        order = [-1]*N
        ids = [0]*N
        parent = [-1]*N
        stack = deque()
        for i in range(N):
            if order[i] == -1:
                stack.append(i)
                stack.append(i)
                while stack:
                    v = stack.pop()
                    if order[v] == -1:
                        low[v] = order[v] = now_ord
                        now_ord += 1
                        visited.append(v)
                        for i in range(g.start[v],g.start[v+1]):
                            to = g.elist[i]
                            if order[to] == -1:
                                stack.append(to)
                                stack.append(to)
                                parent[to] = v
                            else:
                                low[v] = min(low[v],order[to])
                    else:
                        if low[v] == order[v]:
                            while True:
                                u = visited.pop()
                                order[u] = N
                                ids[u] = group_num
                                if u == v:
                                    break
                            group_num += 1
                        if parent[v] != -1:
                            low[parent[v]] = min(low[parent[v]],low[v])
        for i,x in enumerate(ids):
            ids[i] = group_num-1-x

        return group_num,ids
    
    def scc(self):
        group_num,ids = self.scc_ids()
        groups = [[] for _ in range(group_num)]
        for i,x in enumerate(ids):
            groups[x].append(i)
        return groups
    
import sys
readline = sys.stdin.buffer.readline
read = sys.stdin.buffer.read
N,M = map(int,readline().split())
ab = list(map(int,read().split()))
sg = scc_graph(N)

it = iter(ab)
for a,b in zip(it,it):
    sg.add_edge(a,b)

scc = sg.scc()
print(len(scc))
for group in scc:
    print(str(len(group))+' '+' '.join(map(str,group)))