Problem p03026 (python)

Fixed submission:
class Queue(object):

    def __init__(self):
        self.queue_list = []

    def enqueue(self, value):
        self.queue_list.append(value)

    def dequeue(self):
        try:
            # 先頭をとりだす
            value = self.queue_list.pop(0)
        except IndexError:
            value = None

        return value
N = int(input())

pair = []
tree = {}

for _ in range(N-1):
    a, b = list(map(int, input().split(" "))) 
    if a in tree.keys():
        tree[a].append(b)
    else:
        tree[a] = [b]
        
    if b in tree.keys():
        tree[b].append(a)
    else:
        tree[b] = [a]
    pair.append([a,b])
    
c = list(map(int, input().split(" ")))
c.sort(reverse=True)
c = c[:N+2]


queue = Queue()
tree_l = {}
for key in tree.keys():
    tree_l[key] = len(tree[key])

ans = {}
max_node = max((v, k) for k, v in tree_l.items())[1]
ans[max_node] = c[0]
used = [max_node]
cnt = 0

candi = {}
for i in tree[max_node]:
    candi[i] = tree_l[i]

for k, v in sorted(candi.items(), key=lambda x: -x[1]):
    queue.enqueue(k)
    used.append(k)

while True:
    node = queue.dequeue()
    cnt += 1
    ans[node] = c[cnt]
    
    if cnt == N-1:
        break
    
    candi = {}
    for i in tree[node]:
        candi[i] = tree_l[i]
    for k, v in sorted(candi.items(), key=lambda x: -x[1]):
        if k not in used:
            queue.enqueue(k)
            used.append(k)
total = 0
for a, b in pair:
    if ans[a] > ans[b]:
        total += ans[b]
    else:
        total += ans[a]
        
print(total)
for i in range(1, N, 1):
    print(ans[i], end=" ")

print(ans[N])

Buggy submission (verdict: Runtime Error):
class Queue(object):

    def __init__(self):
        self.queue_list = []

    def enqueue(self, value):
        self.queue_list.append(value)

    def dequeue(self):
        try:
            # 先頭をとりだす
            value = self.queue_list.pop(0)
        except IndexError:
            value = None

        return value
N = int(input())

pair = []
tree = {}

for _ in range(N-1):
    a, b = list(map(int, input().split(" "))) 
    if a in tree.keys():
        tree[a].append(b)
    else:
        tree[a] = [b]
        
    if b in tree.keys():
        tree[b].append(a)
    else:
        tree[b] = [a]
    pair.append([a,b])
    
c = list(map(int, input().split(" ")))
c.sort(reverse=True)
c = c[:N+2]

queue = Queue()
tree_l = {}
for key in tree.keys():
    tree_l[key] = len(tree[key])

ans = {}
max_node = max((v, k) for k, v in tree_l.items())[1]
ans[max_node] = c[0]
used = [max_node]
cnt = 0

candi = {}
for i in tree[max_node]:
    candi[i] = tree_l[i]

for k, v in sorted(candi.items(), key=lambda x: -x[1]):
    queue.enqueue(k)

while True:
    node = queue.dequeue()
    cnt += 1
    ans[node] = c[cnt]
    
    if cnt == N-1:
        break
    
    candi = {}
    for i in tree[node]:
        candi[i] = tree_l[i]
    for k, v in sorted(candi.items(), key=lambda x: -x[1]):
        if k not in used:
            queue.enqueue(k)

            
total = 0
for a, b in pair:
    if ans[a] > ans[b]:
        total += ans[b]
    else:
        total += ans[a]
        
print(total)
for i in range(1, N, 1):
    print(ans[i], end=" ")

print(ans[N])