DFS

def fun(i,adj,visited,ans):
    visited[i]=True
    ans.append(i)
    for neigh in adj[i]:
        if not visited[neigh]:
            fun(neigh,adj,visited,ans)

class Solution:
    def dfs(self, adj):
        ans=[]
        visited=[False]*len(adj)
        for i in range(len(adj)):
            if not visited[i]:
                fun(i,adj,visited,ans)
        return ans