Hi,

I am stuck at 2001D - Longest Max Min Subsequence. My logic is similar to other accepted solutions. Also, my solution works for all the small test cases I can find from other people's accepted solutions. Some test cases are big and thus not present in complete form.

Can someone please point out the bug/ provide a test case for which the code does not work?

Thanks in advance.

import heapq


def solve(nums):
    uq = set()
    cum = [0] * len(nums)
    for i, v in enumerate(nums[::-1]):
        uq.add(v)
        cum[i] = len(uq)
    cum = cum[::-1]

    min_heap, max_heap = [], []
    for i, v in enumerate(nums):
        heapq.heappush(min_heap, (-cum[i], v, i))
        heapq.heappush(max_heap, (-cum[i], -v, i))

    last_idx = -1
    ans, used = [], set()
    for i in range(len(uq)):
        if i%2: # pick small
            while min_heap and (min_heap[0][2] < last_idx or min_heap[0][1] in used):
                heapq.heappop(min_heap)
            now = heapq.heappop(min_heap)
            ans.append(now[1])
            used.add(now[1])
            last_idx = now[2]
            continue

        while max_heap and (max_heap[0][2] < last_idx or -max_heap[0][1] in used):
            heapq.heappop(max_heap)
        now = heapq.heappop(max_heap)
        ans.append(-now[1])
        used.add(-now[1])
        last_idx = now[2]

    return ans

if __name__ == '__main__':
    for _ in range(int(input())):
        n = int(input())
        num = list(map(int, input().split()))

        ans_ = solve(num)
        print(len(ans_))
        print(*ans_)