题解 | 机器翻译

max_num, n = map(int,input().split())
li = []
se = set()
left = right = step = 0
li2 = list(map(int,input().split()))
for i in li2:
    if i in se:
        continue
    if right-left >= max_num:
        se.remove(li[left])
        left += 1
    se.add(i)
    li.append(i)
    right+=1
    step +=1
print(step)