Problem: 2063C - Remove Exactly Two
Language: python

Solution 1 (runtime: 781 ms):
t = int(input())

for x in range(t):
    n = int(input())
    edges = []
    adj_list = []

    for y in range(n+1):
        adj_list.append([])

    for e in range(n-1):
        a,b = list(map(int, input().split(" ")))
        
        adj_list[a].append(b)
        adj_list[b].append(a)


    for i in range(2):
        cnt_max_edges = 0
        max_edges = []
        for node in range(1, n+1):
            if adj_list[node] != None:
                if len(adj_list[node]) > cnt_max_edges:
                    cnt_max_edges = len(adj_list[node])
                    max_edges = [node]
                elif len(adj_list[node]) == cnt_max_edges:
                    max_edges.append(node)


        if len(max_edges) <= 2 or i == 1:
            max_edges = [max_edges[0]]
        else:
            f = False
            for idx1 in range(0, len(max_edges)):
                if f: break
                for idx2 in range(idx1+1, len(max_edges)):
                    if not max_edges[idx2] in adj_list[max_edges[idx1]]:
                        max_edges = [max_edges[idx1], max_edges[idx2]]
                        f = True
                        break


        for most_edges_node in max_edges:
            for node in adj_list[most_edges_node]:
                adj_list[node].remove(most_edges_node)

            adj_list[most_edges_node] = None

        if len(max_edges) >= 2:
            break

    count_cc = 0
    connected = {}
    v = 1
    for node in range(1, n+1):
        if adj_list[node] != None and not node in connected:
            queue = [node]

            while len(queue) > 0:
                curr = queue.pop()
                connected[curr] = count_cc
                for adj_node in adj_list[curr]:
                    if not adj_node in connected:
                        queue.append(adj_node)
                        connected[adj_node] = count_cc

            count_cc += 1

    print(count_cc)

Solution 2 (runtime: 765 ms):
import sys, os, io
input = io.BytesIO(os.read(0, os.fstat(0).st_size)).readline

def solve646():
    n = int(input())
    e = []
    for _ in range(n-1):
        u, v = map(int, input().split())
        u, v = u-1, v-1
        e.append([u, v])
    final_res = 0
    for _ in range(2):
        adj = [[] for _ in range(n)]
        for u, v in e:
            adj[u].append(v)
            adj[v].append(u)
        rm = [False] * n
        d = [0] * n
        for i in range(n):
            d[i] = len(adj[i])
        for _ in range(2):
            mx = u = -1
            for i in range(n):
                if not rm[i] and mx < d[i]:
                    mx = d[i]
                    u = i
            rm[u] = True
            d[u] = 0
            for v in adj[u]:
                d[v] -= 1
        res = 0
        visited = rm[:]
        def dfs(u):
            visited[u] = True
            q = [u]
            while q:
                u = q.pop()
                for v in adj[u]:
                    if not visited[v]:
                        visited[v] = True
                        q.append(v)
        for i in range(n):
            if not visited[i]:
                dfs(i)
                res += 1
        final_res = max(final_res, res)
        for i, edge in enumerate(e):
            u, v = edge
            e[i] = [n-1-u, n-1-v]
    return final_res

res_test = []
for _ in range(int(input())):
    res_test.append(solve646())
    
sys.stdout.write("\n".join(map(str, res_test))) #output all test