Problem p03354 (python)

Fixed submission:
import sys
input = sys.stdin.buffer.readline
N,M = list(map(int,input().split()))
p = [i-1 for i in map(int,input().split())]
alr = [False for i in range(N)]
xy = [[] for i in range(N)]
for i in range(M):
    x,y = map(int,input().split())
    x -= 1
    y -= 1
    xy[x].append(y)
    xy[y].append(x)
count = 0

for i in range(N):
    if (not alr[i]) and (xy[i]):
        alr[i] = True
        stack = [i]
        numlist = set()
        numlist.add(i)
        while stack:
            j = stack.pop()
            for k in xy[j]:
                if not alr[k]:
                    alr[k] = True
                    stack.append(k)
                    numlist.add(k)
        indlist = set([p[i] for i in numlist])
        count += len(numlist & indlist)
    else:
        if (not alr[i]) and p[i] == i:
            count += 1
print(count)

Buggy submission (verdict: Runtime Error):
N,M = list(map(int,input().split()))
p = list(map(int,input().split()))
p = [i-1 for i in p]
rem = [True for i in range(N)]
xy = [[] for i in range(N)]
for i in range(M):
    x,y = list(map(int,input().split()))
    x -= 1
    y -= 1
    xy[x].append((y,p.index(y)))
    xy[y].append((x,p.index(x)))
    rem[x] = False
    rem[y] = False
count = 0
for i in range(N):
    if rem[i] and p[i] == i:
        count += 1
alr = rem.copy()
for i in range(N):
    if (not alr[i]) and (xy[i]):
        alr[i] = True
        stack = [j for j in xy[i]]
        indlist = [p.index(i)]
        numlist = [i]
        while stack:
            num,ind = stack.pop()
            alr[num] = True
            numlist.append(num)
            indlist.append(ind)
            for j in xy[num]:
                if not alr[j[0]]:
                    alr[j[0]] = True
                    stack.append(j)
        for num in numlist:
            if num in indlist:
                count += 1
print(count)

Buggy submission (verdict: Runtime Error):
N,M = list(map(int,input().split()))
p = list(map(int,input().split()))
p = [i-1 for i in p]
rem = [True for i in range(N)]
xy = [[] for i in range(N)]
for i in range(M):
    x,y = list(map(int,input().split()))
    x -= 1
    y -= 1
    xy[x].append((y,p.index(y)))
    xy[y].append((x,p.index(x)))
    rem[x] = False
    rem[y] = False
count = 0
for i in range(N):
    if rem[i] and p[i] == i:
        count += 1
alr = rem.copy()
for i in range(N):
    if (not alr[i]) and (xy[i]):
        alr[i] = True
        stack = [j for j in xy[i]]
        indlist = [j[1] for j in xy[i]]
        numlist = [j[0] for j in xy[i]]
        while stack:
            num,ind = stack.pop()
            alr[num] = True
            numlist.append(num)
            indlist.append(ind)
            for j in xy[num]:
                if not alr[j[0]]:
                    alr[j[0]] = True
                    stack.append(j)
        for num in numlist:
            if num in indlist:
                count += 1
print(count)

Buggy submission (verdict: Runtime Error):
N,M = list(map(int,input().split()))
p = list(map(int,input().split()))
p = [i-1 for i in p]
rem = [True for i in range(N)]
xy = [[] for i in range(N)]
for i in range(M):
    x,y = list(map(int,input().split()))
    x -= 1
    y -= 1
    xy[x].append((y,p.index(y)))
    xy[y].append((x,p.index(x)))
    rem[x] = False
    rem[y] = False
count = 0
for i in range(N):
    if rem[i] and p[i] == i:
        count += 1
alr = rem.copy()
for i in range(N):
    if (not alr[i]) and (xy[i]):
        alr[i] = True
        stack = [*xy[i]]
        indlist = [i[0] for i in xy[i]]
        numlist = [i[1] for i in xy[i]]
        while stack:
            num,ind = stack.pop()
            alr[num] = True
            numlist.append(num)
            indlist.append(ind)
            for j in xy[num]:
                if not alr[j[0]]:
                    alr[j[0]] = True
                    stack.append(j)
        for num in numlist:
            if num in indlist:
                count += 1
print(count)