有序数列去除重复项

# 有序数列


def fun1(li: list):
    return len(set(li))


def fun2(li: list):
    new = []
    for i in li:
        if i not in new:
            new.append(i)
    return len(new)


def fun3(li: list):
    i = 0
    for j in range(1, len(li)):
        if li[i] != li[j]:
            i += 1
            li[i] = li[j]
    return i + 1


li = [1, 2, 3, 3, 4, 5, 5, 5, 5, 6]
print(fun1(li))
print(fun2(li))
print(fun3(li))