[백준] 바이러스

Initial code was this

from collections import defaultdict, deque

n = int(input())
cons = int(input())
graph = defaultdict(list)
for _ in range(cons):
    start,end = map(int,input().split())
    graph[start].append(end)
    graph[end].append(start)

visited=[False for _ in range(n)]
global ans
ans = 0

def dfs(i,visited,graph):
    global ans 
    visited[i]=True
    for node in graph[i]:
        if not visited[node]:
            dfs(node,visited,graph)
            ans +=1

dfs(1,visited,graph)
print(ans)
indexerror

but I got a IndexError error.
My dfs logic is right but while the input graph that I am getting is not 0-indexed (it starts from node 1 and not node 0), I was wrongly assigning my visited list as 0-indexed of size n. It should be size n+1 to accomodate for 1 more element since it is not 0-indexed.

So fixing

visited=[False for _ in range(n+1)]

made it right