Problem:


Problem Statement

We have N boxes, numbered 1 through N. At first, box 1 contains one red ball, and each of the other boxes contains one white ball.

Snuke will perform the following M operations, one by one. In the i-th operation, he randomly picks one ball from box x_i, then he puts it into box y_i.

Find the number of boxes that may contain the red ball after all operations are performed.

Constraints

2≤N≤10^5

1≤M≤10^5

1≤x_i,y_i≤N

x_i≠y_i

Just before the i-th operation is performed, box x_i contains at least 1 ball.

Input

The input is given from Standard Input in the following format:

N M
x_1 y_1
:
x_M y_M

Output

Print the number of boxes that may contain the red ball after all operations are performed.

Sample Input 1

3 2
1 2
2 3

Sample Output 1

2

Just after the first operation, box 1 is empty, box 2 contains one red ball and one white ball, and box 3 contains one white ball.

Now, consider the second operation. If Snuke picks the red ball from box 2, the red ball will go into box 3. If he picks the white ball instead, the red ball will stay in box 2.
Thus, the number of boxes that may contain the red ball after all operations, is 2.

Sample Input 2

3 3
1 2
2 3
2 3

Sample Output 2

1

All balls will go into box 3.

Sample Input 3

4 4
1 2
2 3
4 1
3 4

Sample Output 3

3



Sample input:
3 2
1 2
2 3


Sample output:
2

Submission status: Accepted

Solution code:
import sys

input_methods=['clipboard','file','key']
using_method=0
input_method=input_methods[using_method]

tin=lambda : map(int, input().split())
lin=lambda : list(tin())
mod=1000000007

#+++++

def main():
	#a = int(input())
	n, m = tin()
	#s = input()
	is_red_in = [0]*n
	is_red_in[0] = 1
	num_of_ball = [1] * n
	for _ in range(m):
		f, t = tin()
		f, t = f-1, t-1
		num_of_ball[f] -= 1
		num_of_ball[t] += 1
		if is_red_in[f] == 1:
			is_red_in[t] = 1
		if num_of_ball[f] == 0:
			is_red_in[f] = 0
	return sum(is_red_in)
	
	
#+++++
isTest=False

def pa(v):
	if isTest:
		print(v)
		
def input_clipboard():
	import clipboard
	input_text=clipboard.get()
	input_l=input_text.splitlines()
	for l in input_l:
		yield l

if __name__ == "__main__":
	if sys.platform =='ios':
		if input_method==input_methods[0]:
			ic=input_clipboard()
			input = lambda : ic.__next__()
		elif input_method==input_methods[1]:
			sys.stdin=open('inputFile.txt')
		else:
			pass
		isTest=True
	else:
		pass
		#input = sys.stdin.readline
			
	ret = main()
	if ret is not None:
		print(ret)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
box = [1] * n
red = [0] * n
red[0] = 1
for i in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1

    if box[a]:
        if red[a] == 1:
            red[b] = 1

        if box[a] == 1:
            if red[a] == 1:
                red[a] = 0

        box[a] -= 1
        box[b] += 1

print(sum(red))

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
box = [1]*(n+1)
red = [False]*(n+1)
red[1] = True

for i in range(m):
    x, y = map(int, input().split())
    if red[x]:
        red[y] = True
    box[x] -= 1
    box[y] += 1
    if box[x] == 0:
        red[x] = False

print(red.count(True))

Submission status: Accepted

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())
c = [1]*n
r = set([0])
for i in range(m):
    x,y = map(int, input().split())
    x -= 1
    y -= 1
    if c[x]==1 and x in r:
        r.remove(x)
        r.add(y)
    elif c[x]>=2 and x in r:
        r.add(y)
    c[x] -= 1
    c[y] += 1
print(len(r))

Submission status: Accepted

Solution code:
import math
import collections
import fractions
import itertools
import functools
import  operator

def solve():
    n, m = map(int, input().split())
    ball, can = [1]*n, [False]*n
    can[0] = True
    for _ in range(m):
        x, y = map(int, input().split())
        if can[x-1] == True:
            can[y-1] = True
        ball[x-1] -= 1
        ball[y-1] += 1
        if ball[x-1] == 0:
            can[x-1] = False
    print(can.count(True))
    return 0

if __name__ == "__main__":
    solve()

Submission status: Accepted

Solution code:
N,M = map(int,input().split())
C = {i:[1,0] for i in range(1,N+1)}
C[1] = [1,1]
for _ in range(M):
    x,y = map(int,input().split())
    C[y][0] += 1
    if C[x][1]==1:
        C[y][1] = 1
    C[x][0] -= 1
    if C[x][0]==0:
        C[x][1]=0
cnt = 0
for i in range(1,N+1):
    if C[i][1]==1:
        cnt += 1
print(cnt)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
C = [0]*(n+1)
C[1] = 1
D = [1]*(n+1)
for _ in range(m):
  x, y = map(int, input().split())
  if C[x]:
    C[y] = 1
    if D[x] == 1:
      C[x] = 0
  D[x] -= 1
  D[y] += 1
ans = sum(C)
print(ans)

Submission status: Accepted

Solution code:
n,m = map(int, input().split())
xy = [list(map(int, input().split())) for _ in range(m)]

box = [1]*(n+1)
red = [0]*(n+1)
red[1] = 1
for x,y in xy:
    box[x] -= 1
    box[y] += 1
    if red[x]==1: red[y] = 1
    if box[x]==0: red[x] = 0
print(sum(red))

Submission status: Accepted

Solution code:
import sys

sys.setrecursionlimit(10 ** 8)
ini = lambda: int(sys.stdin.readline())
inm = lambda: map(int, sys.stdin.readline().split())
inl = lambda: list(inm())
ins = lambda: sys.stdin.readline().rstrip()
debug = lambda *a, **kw: print("\033[33m", *a, "\033[0m", **dict(file=sys.stderr, **kw))

N, M = inm()


def solve():
    pos = {0}
    count = [1] * N
    for i in range(M):
        x, y = inm()
        x -= 1
        y -= 1
        if x in pos:
            if count[x] == 1:
                pos.remove(x)
            pos.add(y)
        count[x] -= 1
        count[y] += 1
    return len(pos)


print(solve())

Submission status: Accepted

Solution code:
N,M=map(int,input().split())
X=[0]*(N+1)
X[1]=1
Y=[1]*(N+1)
a,b=0,0
for i in range(M):
  a,b=map(int,input().split())
  X[b]|=X[a]
  Y[b]+=1
  Y[a]-=1
  if Y[a]==0:
    X[a]=0
print(sum(X))

Submission status: Accepted

Solution code:
N, M = map(int, input().split())

red = [0]*N
red[0] = 1
white = [1]*N
white[0] = 0
ans = 1
for i in range(M):
    a, b = map(int, input().split())
    if red[a-1] == 1:
        if red[b-1] == 0:
            red[b-1] += 1
            ans += 1
        else:
            white[b-1] += 1

        if white[a-1] > 0:
            white[a-1] -= 1
        else:
            red[a-1] -= 1
            ans -= 1
    elif white[a-1] > 0:
        white[a-1] -= 1
        white[b-1] += 1
print(ans)

Submission status: Accepted

Solution code:
import sys
import math
import itertools
import bisect
from copy import copy
from collections import deque,Counter
from decimal import Decimal
def s(): return input()
def i(): return int(input())
def S(): return input().split()
def I(): return map(int,input().split())
def X(): return list(input())
def L(): return list(input().split())
def l(): return list(map(int,input().split()))
def lcm(a,b): return a*b//math.gcd(a,b)
def gcd(*numbers): reduce(math.gcd, numbers)
sys.setrecursionlimit(10 ** 9)
mod = 10**9+7
count = 0
ans = 0

N, M = I()
a = []
c = [1]*N
red = [0]*N
red[0] = 1

for i in range(M):
    x = l()
    a.append(x)
    c[x[0]-1] -= 1
    c[x[1]-1] += 1
    if red[x[0]-1]:
        red[x[1]-1] = 1
    if not c[x[0]-1]:
        red[x[0]-1] = 0


print(sum(red))

Submission status: Accepted

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

for i in range(m):
    x = []
    x = list(map(int,input().split()))
    b_list.append(x)

ans_list = [0 for i in range(10**5)]
ans_list[0] = 1
ball_list = [1 for i in range(10**5)]

for tmp in b_list:
    x, y = tmp[0], tmp[1]
    if ans_list[x-1] == 1 and ans_list[y-1] == 0:
        ans_list[y-1] += 1
    ball_list[y-1] += 1
    ball_list[x-1] -= 1
    if ball_list[x-1] == 0:
        ans_list[x-1] = 0

ans = 0

for i in ans_list:
    if i == 1:
        ans += 1

print(ans)

Submission status: Accepted

Solution code:
from sys import stdin


def main():
    input = lambda: stdin.readline()[:-1]
    N, M = map(int, input().split())
    XY = [tuple(map(int, input().split())) for _ in [0] * M]

    box = [1] * (N + 1)
    red = [0] * (N + 1)
    box[0], red[1] = 0, 1
    for x, y in XY:
        box[x] -= 1
        box[y] += 1
        if red[x]:
            red[y] = 1
        if not box[x]:
            red[x] = 0
    print(sum(red))


main()

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
flg=[False for i in range(n)]
flg[0]=True
t=[1 for i in range(n)]
tmp=1
for i in range(m):
    x,y=map(int,input().split())
    x,y=x-1,y-1
    t[x]-=1
    t[y]+=1
    if flg[x]:
        flg[y]=True
        if t[x]==1 and len(flg)==1:
            flg[x]=False

    if t[x]==0:
        flg[x]=False
ans=0
for i in range(n):
    if flg[i]:
        ans+=1
print(ans)

Submission status: Accepted

Solution code:
from collections import defaultdict

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

ball_count=[1 for _ in range(N)]
redExist=[0 for _ in range(N)]
redExist[0]=1
for m in range(M):
  x, y = map(int, input().split())
  #1オリジンから0オリジンに
  x-=1
  y-=1

  ball_count[x] -= 1
  ball_count[y] += 1
  if (redExist[x]):
    redExist[y]=True
  if ball_count[x] == 0:
    redExist[x]=False
print(len([b for b in redExist if b]))

Submission status: Accepted

Solution code:
from collections import Counter,defaultdict,deque
from heapq import heappop,heappush,heapify
import sys,bisect,math,itertools,fractions,pprint
sys.setrecursionlimit(10**8)
mod = 10**9+7
INF = float('inf')
def inp(): return int(sys.stdin.readline())
def inpl(): return list(map(int, sys.stdin.readline().split()))

n,m = inpl()
res = [False] * n
res[0] = True
cnt = [1] * n
for i in range(m):
    a,b = inpl()
    a,b = a-1,b-1
    cnt[a] -= 1; cnt[b] += 1
    if res[a]:
        res[b] = True
    if cnt[a] == 0:
        res[a] = False
print(sum(res))

Submission status: Accepted

Solution code:
#from statistics import median
#import collections
#aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]
from fractions import gcd
from itertools import combinations,permutations,accumulate # (string,3) 3回
#from collections import deque
from collections import deque,defaultdict,Counter
import decimal
import re
#import bisect
#
#    d = m - k[i] - k[j]
#    if kk[bisect.bisect_right(kk,d) - 1] == d:
#
#
#
# pythonで無理なときは、pypyでやると正解するかも！！
#
#

import sys
sys.setrecursionlimit(10000000)
mod = 10**9 + 7
#mod = 9982443453
def readInts():
  return list(map(int,input().split()))
def I():
  return int(input())
n,m = readInts()
box = [1] * n
nya = [True] + [False]*(n-1)
for i in range(m):
    x,y = map(lambda x:int(x)-1,input().split())
    # if box[x] < 2:
    #     if nya[x] == True:
    #         if box[x]-1 == 0:
    #             nya[x] = False
    #         nya[y] = True
    #     else:
    #         nya[y] = False
    #     box[x] -= 1
    #     box[y] += 1
    # else:
    #     nya[y] = True
    #     box[x] -= 1
    #     box[y] += 1
    box[x] -= 1
    box[y] += 1
    if nya[x]:
        nya[y] = True
    if box[x] == 0:
        nya[x] = False
print(nya.count(True))

Submission status: Accepted

Solution code:
def solve():
    ans = 0
    N, M = map(int, input().split())
    lis = [1]*N
    lis[0] = -1 #赤が入っている可能性があればマイナス
    for _ in range(M):
        x,y = map(int, input().split())
        x -= 1
        y -= 1
        if lis[x]<0:
            lis[y] = -(abs(lis[y])+1)
            lis[x] += 1
        else:
            if lis[y]==0:
                lis[y] = 1
            else:
                lis[y] = (abs(lis[y])+1)*lis[y]//abs(lis[y])
            lis[x] -= 1
    ans = sum(map(lambda x:x<0,lis))
    return ans
print(solve())

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
red = [0]*n
ball = [1]*n
red[0] = 1
for i in range(m):
    x, y = map(int, input().split())
    if red[x-1] == 1:
        red[y-1] = 1
        if ball[x-1] == 1:
            red[x-1] = 0
    ball[y-1] += 1
    ball[x-1] -= 1
print(sum(red))

Submission status: Accepted

Solution code:
N,M = map(int,input().split())
A = [0 for _ in range(N+1)]
B = [1 for _ in range(N+1)]
A[1] = 1
B[0] = 0
for _ in range(M):
    x,y = map(int,input().split())
    if A[x]==1:
        A[y]=1
    B[y] += 1
    B[x] -= 1
    if B[x]==0:
        A[x] = 0
print(sum(A))

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)

N, M = map(int, input().split())
red = [0] * (N + 1)
white = [1] * (N + 1)
red[1] = 1
white[1] = 0

for _ in range(M):
    x, y = map(int, input().split())
    if red[x]:
        red[y] += 1
    else:
        white[y] += 1
    if white[x]:
        white[x] -= 1
    else:
        red[x] -= 1

print(N-red[1:].count(0))

Submission status: Accepted

Solution code:
N,M = map(int,input().split())

ans = [0]*N
ans[0] = 1
ball = [1]*N

for _ in range(M):
    x,y = map(int,input().split())
    x -= 1
    y -= 1
    if ans[x]:
        ans[y] = 1
    ball[x] -= 1
    ball[y] += 1

    if not ball[x]:
        ans[x] = 0

print(sum([i*(j>0) for i,j in zip(ans,ball)]))

Submission status: Accepted

Solution code:
n,m = map(int, input().split())
xy = [list(map(int, input().split())) for _ in range(m)]

box = [1]*(n+1)
red = [0]*(n+1)
red[1] = 1
for x,y in xy:
    box[x] -= 1
    box[y] += 1
    if red[x] == 1: red[y] = 1
    if box[x] == 0: red[x] = 0
print(red.count(1))

Submission status: Accepted

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

X = [0]*n
C = [1]*n
X[0] = 1

for i in range(m):
    x, y = map(int, input().split())
    x, y = x-1, y-1
    if X[x] == 1:
        X[y] = 1
        if C[x] == 1:
            X[x] = 0
        C[x] -= 1
        C[y] += 1
    else:
        C[x] -= 1
        C[y] += 1

ans = sum(X)
print(ans)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
num = [1] * n
red = [False] * n
red[0] = True
for _ in range(m):
    x, y = map(int, input().split())
    x -= 1
    y -= 1
    if red[x]:
        red[y] = True
    num[x] -= 1
    num[y] += 1
    if num[x] == 0:
        red[x] = False
ans = 0
for r in red:
    ans += r
print(ans)

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
li = [list(map(int, input().split())) for _ in range(m)]

ball_cnt = [1] * 10**6
check = [0] * 10**6

check[1] += 1

for i in range(m):
    x = li[i][0]
    y = li[i][1]
    
    if check[x] == 1:
        check[y] = 1
    
    ball_cnt[x] -= 1
    ball_cnt[y] += 1
    
    if ball_cnt[x] == 0:
        check[x] = 0
        
print(sum(check))

Submission status: Accepted

Solution code:
# https://atcoder.jp/contests/agc002/tasks/agc002_b
import sys
sys.setrecursionlimit(1 << 25)
read = sys.stdin.readline
ra = range
enu = enumerate


def mina(*argv, sub=1): return list(map(lambda x: x - sub, argv))
# 受け渡されたすべての要素からsubだけ引く.リストを*をつけて展開しておくこと


def read_a_int(): return int(read())


def read_ints(): return list(map(int, read().split()))


def read_col(H):
    '''H is number of rows
    A列、B列が与えられるようなとき
    ex1)A,B=read_col(H)    ex2) A,=read_col(H) #一列の場合'''
    ret = []
    for _ in range(H):
        ret.append(list(map(int, read().split())))
    return tuple(map(list, zip(*ret)))


N, M = read_ints()
X, Y = read_col(M)
X = mina(*X)
Y = mina(*Y)
# 有向グラフでつないで1からbfsで到達するノードの数を記録する？#順序情報が消えてしまう
# ただ単純に赤の可能性のある配列を用意しておけばいいんじゃない？
# ボールの個数も管理しないと
prob = [False] * N
n_balls = [1] * N
prob[0] = True

for x, y in zip(X, Y):
    prob[y] = prob[y] or prob[x]
    n_balls[x] -= 1
    n_balls[y] += 1
    if n_balls[x] == 0:
        prob[x] = False


print(sum(prob))

Submission status: Accepted

Solution code:
import numpy as np

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

box = np.array([1]*N)#個数
pos = np.array([0]*N)#ありえるか
pos[0] = 1

for i in range(M):
    x, y = map(lambda x:int(x)-1,input().split())
    box[x] -= 1
    box[y] += 1
    if pos[x]:
        pos[y] = 1
        if box[x] == 0:
            pos[x] = 0

#print(box)
#print(pos)

box = np.where(box > 0, 1, 0)
print(sum(pos*box))

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
l=[1]+[0]*(n+1)
a=[1]*n
for i in range(m):
 x,y=map(int,input().split())
 if l[x-1]:l[y-1]=1
 a[x-1]-=1;a[y-1]+=1
 if not a[x-1]:l[x-1]=0
print(l.count(1))

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
xy = [list(map(int, input().split())) for _ in range(m)]
l=[1]*n
out_=[0]*n
in_=[0]*n
c=1

check=0
for i in range(m):
    if check==0:
        if xy[i][0]==1:
            in_[xy[i][1]-1]+=1
            check=1
        else:
            if xy[i][1]==1:
                in_[xy[i][1]-1]+=1
                check=1
        l[xy[i][0]-1]-=1
        l[xy[i][1]-1]+=1
    else:
        l[xy[i][0]-1]-=1
        l[xy[i][1]-1]+=1
        if l[xy[i][0]-1]==0 and in_[xy[i][0]-1]!=0:
            in_[xy[i][0]-1]=0
            in_[xy[i][1]-1]+=1
        elif l[xy[i][0]-1]!=0 and in_[xy[i][0]-1]!=0:
            in_[xy[i][1]-1]+=1
ans=0
for i in range(n):
    if in_[i]!=0:
        ans+=1
print(ans)

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
xy = [list(map(int, input().split())) for _ in range(m)]
l=[1]*n
out_=[0]*n
in_=[0]*n#入れられたことがある履歴。0番目だけは初期値1
c=1
#print(in_)
check=0
for i in range(m):
    if check==0:
        if xy[i][0]==1:#箱1に入ってくる前に初めて箱1から赤いボールを移す場合
            in_[xy[i][1]-1]+=1
            check=1
        else:#箱１から赤いボールを移す前に白いボールが入ってくる場合
            if xy[i][1]==1:
                in_[xy[i][1]-1]+=1
                check=1
        l[xy[i][0]-1]-=1
        l[xy[i][1]-1]+=1
        #print(l,in_)
    else:
        l[xy[i][0]-1]-=1
        l[xy[i][1]-1]+=1
        if l[xy[i][0]-1]==0 and in_[xy[i][0]-1]!=0:#移した後、空になる場合
            in_[xy[i][0]-1]=0
            in_[xy[i][1]-1]+=1
        elif l[xy[i][0]-1]!=0 and in_[xy[i][0]-1]!=0:#移した後、残っている場合
            in_[xy[i][1]-1]+=1
        #print(l,in_)
#print(l,in_)
ans=0
for i in range(n):
    if in_[i]!=0:
        ans+=1
print(ans)

Submission status: Accepted

Solution code:
N,M=map(int,input().split())
R=[True]+[False]*(N-1)
B=[1]*N
for i in range(M):
    x,y=map(int,input().split())
    if R[x-1]:
        R[y-1]=True
    B[x-1]-=1
    B[y-1]+=1
    if B[x-1]==0:
        R[x-1]=False
print(R.count(True))

Submission status: Accepted

Solution code:
import sys

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N, M = map(int, readline().split())
m = map(int, read().split())

count = [1] * (N+1)
red = [0] * (N+1)
red[1] = True
for x, y in zip(m, m):
    count[x] -= 1
    count[y] += 1
    if red[x]:
        red[y] = 1
    if not count[x]:
        red[x] = 0

print(sum(red))

Submission status: Accepted

Solution code:
def main():
    n,m = map(int,input().split())
    box = [1] * n
    red = [0] * n
    red[0] += 1
    op = [list(map(int,input().split())) for _ in range(m)]
    for o in op:
        x, y = o[0]-1, o[1]-1
        if box[x] < 1:
            continue
        box[x] -= 1
        if red[x] > 0:
            red[y] = 1
        if box[x] == 0:
            red[x] = 0
        box[y] += 1
    print(sum(red))

if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
red=[1]+[0]*(n-1)
pink=[1]*n
for _ in range(m):
    x,y=map(int,input().split())
    x-=1
    y-=1
    if red[x] and pink[x]==1:
        red[x]=0
        red[y]=1
    elif red[x] and pink[x]>1:
        red[y]=1
    pink[x]-=1
    pink[y]+=1
print(red.count(1))

Submission status: Accepted

Solution code:
n, m = map(int, input().split())
N = [1]*n
P = [True] + [False]*(n-1)
for i in range(m):
    x, y = list(map(lambda tmp: tmp-1, map(int, input().split())))
    P[y] = True if P[x]==True else P[y]
    N[x] -= 1
    N[y] += 1
    P[x] = False if N[x]==0 else P[x]
print(sum(P))

Submission status: Accepted

Solution code:
n,m = map(int,input().split())
canred = set()
canred.add(1)
balls = [1 for i in range(n)]
for i in range(m):
    x,y = map(int,input().split())
    if x in canred:
        canred.add(y)
    balls[x-1]-=1
    balls[y-1] += 1
    if balls[x-1] == 0:
        canred.discard(x)


print(len(canred))

Submission status: Accepted

Solution code:
#!/usr/bin python3
# -*- coding: utf-8 -*-

def main():
    N, M = map(int, input().split())
    dp = {1:[1,True]}         #dp[i]  iの箱の状態　[x個]赤がいる可能性がある
    for _ in range(2,N+1):
        dp[_] = [1,False]
    for _ in range(M):
        fm, to = map(int, input().split())
        num, state = dp[fm]
        #fmの処理
        dp[fm][0]-=1    #移動
        if dp[fm][0]==0:
            dp[fm][1] = False
        #toの処理
        dp[to][0]+=1    #移動
        dp[to][1]=dp[to][1] or state
    ret = 0
    for _ in range(1,N+1):
        ret += dp[_][1]
    print(ret)

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
N, M = map(int, input().split())

Red = [0]*N
Red[0] = 1
Num = [1]*N

for i in range(M):
  In, Out = map(int, input().split())
  In -= 1
  Out -= 1
  Num[In] -= 1
  Num[Out] += 1
  if Red[In]:
    Red[Out] = 1
  if Num[In] == 0:
    Red[In] = 0

print(sum(Red))

Submission status: Accepted

Solution code:
n_box, n_move = map(int,input().split())
num_balls = [1] * n_box
can_red = [0] * n_box
can_red[0] = 1
for i in range(n_move):
    From, to = map(int,input().split())
    From -= 1
    to -= 1
    if can_red[From] == 1:
        if num_balls[From] == 1:
            can_red[From] = 0
            can_red[to] = 1
        else:
            can_red[to] = 1
    num_balls[From] -= 1
    num_balls[to] += 1

ans = 0
for i in range(n_box):
    if can_red[i] == 1:
        ans += 1
print(ans)

Submission status: Accepted

Solution code:
n,m = map(int,input().split(" "))
ar = [[0,1] for i in range(n)]
ar[0] = [1,1]
r = 0
for i in range(m):
    a,b = map(int,input().split(" "))
    a -= 1
    b -= 1
    if ar[a][0] == 1 and ar[a][1] >= 1:
        ar[b][0] = 1
    ar[b][1] += 1
    ar[a][1] -= 1
    if ar[a][1] == 0:
        ar[a][0] = 0
count = 0
for r in ar:
    if r[0] == 1:
        count += 1
print(count)

Submission status: Accepted

Solution code:
'''
Accepted    　:No
difficult   　: 
ペナルティ　  　:5分
実際の回答時間  :分
WAの回数　     :回
合計時間　　  　:分
'''

def myAnswer(N:int,M:int,X:list,Y:list) -> int:
   ans = {0}
   box = [1] * N
   for x,y in zip(X,Y):
      if(x-1 in ans):
         if(box[x - 1]==1):
            ans.remove(x-1)
         ans.add(y-1)
      box[x-1] -= 1
      box[y-1] += 1
   return len(ans)

def modelAnswer():
   return
def main():
   N,M = map(int,input().split())
   X = []
   Y = []
   for _ in range(M):
      x,y=map(int,input().split())
      X.append(x)
      Y.append(y)
   print(myAnswer(N,M,X,Y))
if __name__ == '__main__':
   main()

Submission status: Accepted

Solution code:
n,m = map(int,input().split())
x = [0 for _ in range(m)]
y = [0 for _ in range(m)]
for i in range(m):
    x[i],y[i] = map(int,input().split())
    x[i] -= 1
    y[i] -= 1

box = [1 for _ in range(n)]
red = [0 for _ in range(n)]
red[0] = 1
for i in range(m):
    red[y[i]] = 1 if red[x[i]] else red[y[i]]
    red[x[i]] = red[x[i]] if box[x[i]]-1 else 0
    box[x[i]] -= 1
    box[y[i]] += 1
print(sum(red))

Submission status: Accepted

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

ball = [1]*n
d={}
for i in range(1,n+1):
    d[i]=0
d[1]=1

for _ in range(m):
    x,y = map(int,input().split())

    ball[x-1]-=1
    if d[x]==1:
        if ball[x-1]==0:
            d[x]=0
        d[y]=1
    ball[y-1]+=1

cnt=0
for _ ,v in d.items():
    if v==1:
        cnt+=1


print(cnt)

Submission status: Accepted

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

'''
d = dict()
for i in range(1,n+1):
    d[str(i)] = 1
from collections import deque
ans = deque('1')'''
box = [1 for i in range(n)]
ans = [0 for i in range(n)]
ans[0] = 1
for _ in range(m):
    x,y = map(int,input().split())
    box[x-1] -= 1
    box[y-1] += 1
    if ans[x-1]==1 and ans[y-1]==0:
        ans[y-1] = 1
    if box[x-1]==0 and ans[x-1]==1:
        ans[x-1] = 0
print(sum(ans))

Submission status: Accepted

Solution code:
import sys
n, m = map(int, input().split())
ball = [1 for i in range(n+1)]
box = [0 for i in range(n+1)]
box[1] = 1
for a in sys.stdin.readlines():
    x, y = map(int, a.split())
    ball[x] -= 1
    ball[y] += 1
    if box[y] == 0 and box[x]:
        box[y] = 1
    if box[x] and ball[x] == 0:
        box[x] = 0

print(sum(box))

Submission status: Accepted

Solution code:
n, m = [int(_) for _ in input().split()]

ball = [1 for i in range(n)]
red = [False for i in range(n)]
red[0] = True

for i in range(m):
    x, y = [int(_)-1 for _ in input().split()]
    ball[x] -= 1
    ball[y] += 1
    if red[x]:
        red[y] = True
    if ball[x] == 0:
        red[x] = False

print(sum(red))

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

import math
#from math import gcd
import bisect
from collections import defaultdict
from collections import deque
from collections import Counter
from functools import lru_cache


#############
# Constants #
#############

MOD = 10**9+7
INF = float('inf')
AtoZ = "abcdefghijklmnopqrstuvwxyz"

#############
# Functions #
#############

######INPUT######
def I(): return int(input().strip())
def S(): return input().strip()
def IL(): return list(map(int,input().split()))
def SL(): return list(map(str,input().split()))
def ILs(n): return list(int(input()) for _ in range(n))
def SLs(n): return list(input().strip() for _ in range(n))
def ILL(n): return [list(map(int, input().split())) for _ in range(n)]
def SLL(n): return [list(map(str, input().split())) for _ in range(n)]

######OUTPUT######
def P(arg): print(arg); return
def Y(): print("Yes"); return
def N(): print("No"); return
def E(): exit()
def PE(arg): print(arg); exit()
def YE(): print("Yes"); exit()
def NE(): print("No"); exit()

#####Shorten#####
def DD(arg): return defaultdict(arg)


#####Inverse#####
def inv(n): return pow(n, MOD-2, MOD)

######Combination######
kaijo_memo = []
def kaijo(n):
  if(len(kaijo_memo) > n):
    return kaijo_memo[n]
  if(len(kaijo_memo) == 0):
    kaijo_memo.append(1)
  while(len(kaijo_memo) <= n):
    kaijo_memo.append(kaijo_memo[-1] * len(kaijo_memo) % MOD)
  return kaijo_memo[n]

gyaku_kaijo_memo = []
def gyaku_kaijo(n):
  if(len(gyaku_kaijo_memo) > n):
    return gyaku_kaijo_memo[n]
  if(len(gyaku_kaijo_memo) == 0):
    gyaku_kaijo_memo.append(1)
  while(len(gyaku_kaijo_memo) <= n):
    gyaku_kaijo_memo.append(gyaku_kaijo_memo[-1] * pow(len(gyaku_kaijo_memo),MOD-2,MOD) % MOD)
  return gyaku_kaijo_memo[n]

def nCr(n,r):
  if(n == r):
    return 1
  if(n < r or r < 0):
    return 0
  ret = 1
  ret = ret * kaijo(n) % MOD
  ret = ret * gyaku_kaijo(r) % MOD
  ret = ret * gyaku_kaijo(n-r) % MOD
  return ret

######Factorization######
def factorization(n):
  arr = []
  temp = n
  for i in range(2, int(-(-n**0.5//1))+1):
    if temp%i==0:
      cnt=0
      while temp%i==0: 
        cnt+=1 
        temp //= i
      arr.append([i, cnt])
  if temp!=1:
    arr.append([temp, 1])
  if arr==[]:
    arr.append([n, 1])
  return arr

#####MakeDivisors######
def make_divisors(n):
  divisors = []
  for i in range(1, int(n**0.5)+1):
    if n % i == 0:
      divisors.append(i)
      if i != n // i: 
        divisors.append(n//i)
  return divisors

#####MakePrimes######
def make_primes(N):
  max = int(math.sqrt(N))
  seachList = [i for i in range(2,N+1)]
  primeNum = []
  while seachList[0] <= max:
    primeNum.append(seachList[0])
    tmp = seachList[0]
    seachList = [i for i in seachList if i % tmp != 0]
  primeNum.extend(seachList)
  return primeNum

#####GCD#####
def gcd(a, b):
    while b:
        a, b = b, a % b
    return a

#####LCM#####
def lcm(a, b):
    return a * b // gcd (a, b)

#####BitCount#####
def count_bit(n):
  count = 0
  while n:
    n &= n -1
    count += 1
  return count

#####ChangeBase#####
def base_10_to_n(X, n):
  if X//n:
    return base_10_to_n(X//n, n)+[X%n]
  return [X%n]

def base_n_to_10(X, n):
  return sum(int(str(X)[-i-1])*n**i for i in range(len(str(X))))

#####IntLog#####
def int_log(n, a):
  count = 0
  while n>=a:
    n //= a
    count += 1
  return count

#############
# Main Code #
#############

N,M = IL()
data = ILL(M)
count = [1 for i in range(N)]
p = [0 for i in range(N)]
p[0] = 1
for x,y in data:
  x,y = x-1,y-1
  if count[x] == 1:
    p[y] += p[x]
    p[x] = 0
  else:
    N = count[x]
    p[y] += p[x]
  count[x] -= 1
  count[y] += 1
ans = 0
for i in p:
  if i!=0:
    ans += 1
print(ans)

Submission status: Accepted

Solution code:
N,M=map(int,input().split())
Red=[False]*N
Cnt=[1]*N
Red[0]=True
for i in range(M):
    x,y=map(lambda x:int(x)-1,input().split())
    Red[y]|=Red[x]
    Cnt[y]+=1
    Cnt[x]-=1
    if Cnt[x]==0:
        Red[x]=False
ans=0
for i in range(N):
    if Red[i] and Cnt[i]>0:
        ans+=1
print(ans)

Submission status: Accepted

Solution code:
N, M = map(int, input().split())

ball = [1 for _ in range(N)]
red = [0 for _ in range(N)]
red[0] = 1

now_red = 0

for i in range(M):
    xx, yy = map(int, input().split())
    x = xx-1
    y = yy-1
    
    ball[x] -= 1
    ball[y] += 1
    
    if red[x]:
        if ball[x] == 0:
            red[x] = 0

        red[y] = 1
        now_red = y
    # print("ball", ball)
    # print("red", red)
    # print("now_red", now_red)

print(sum(red))

Submission status: Accepted

Solution code:
n,m=map(int,input().split())
quant=[1]*(n+1)
prob=[0]*(n+1)
prob[1]=1
for i in range(m):
    x,y=map(int,input().split())
    quant[x]-=1
    quant[y]+=1
    if prob[x]>0:
        prob[y]+=1
    if quant[x]==0:
        prob[x]=0

cnt=0
for i in range(n+1):
    if prob[i]>0:
        cnt+=1
print(cnt)

Submission status: Accepted

Solution code:
import numpy as np
import math

n, m = map(int, input().split())
probability = [0 for _ in range(n)]
ball = [1 for _ in range(n)]
probability[0] = 1
for i in range(m):
    x, y = map(int, input().split())
    prob = math.ceil(probability[x-1])
    probability[x-1] = prob * (ball[x-1] - 1) / ball[x-1]
    probability[y-1] += prob / ball[x-1]
    ball[x-1] -= 1
    ball[y-1] += 1
print(np.sum(np.array(probability) > 0))

Submission status: Accepted

Solution code:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2, log
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
from decimal import Decimal
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7
from decimal import *

N, M = MAP()
balls = [[1, 0] for _ in range(N)]  #[white, red]の個数
balls[0] = [0, 1]

for _ in range(M):
	x, y = MAP()

	w_x, r_x = balls[x-1]
	w_y, r_y = balls[y-1]

	if w_x >= 1 and r_x >= 1: 
		balls[x-1][0] -= 1
		balls[y-1][1] += 1

	elif w_x == 0:
		balls[x-1][1] -= 1
		balls[y-1][1] += 1

	else:
		balls[x-1][0] -= 1
		balls[y-1][0] += 1

ans = 0
for i in range(N):
	if balls[i][1]:
		ans += 1
print(ans)