题解 | 预知

n =int(input())
result = []
for i in range(n):
    types = int(input())
    cards = list(map(int,input().split()))
    maxs = max(card for card in cards ) 
    cards.remove(maxs)
    second = 0
    if cards: 
        second = max(card for card in cards)
    if types < 2:
        result.append(-1)
    elif maxs == 1:
        result.append(0)
    elif second == 1:
        result.append(maxs-1)
    else:
        result.append(maxs)


for i in result:
    print(i)

想到哪写到哪反正最后用例测试都过了