from functools import reduce

text = 'Premature optimization is the root of all evil -- DonaldKnuth'

def longest_unique_sequence(sequence):
    i, j, k = 0, 0, set()
    bi, bj = 0, 0
    
    while j < len(sequence):
        if sequence[j] in k:
            k.remove(sequence[i])
            i += 1
        else:
            k.add(sequence[j])
            j += 1

        if j - i > bj - bi:
            bi, bj = i, j

    return bi, bj

def longest_unique_sequence(sequence):
    i, j = 0, 0
    bi, bj = 0, 0
    
    while j < len(sequence):
        if sequence[j] in sequence[i:j]:
            i += 1
        else:
            j += 1
    
        if j - i > bj - bi:
            bi, bj = i, j
            
    return bi, bj

def longest_unique_sequence(sequence):
    i, j = 0, 0
    b = 0, 0, 0
    
    while j < len(sequence):
        k = sequence[j] in sequence[i:j]
        i, j = i + k, j + 1 - k
        b = max(b, (j - i, i, j))

    return slice(b[1], b[2])

def longest_unique_sequence(sequence):
    i, b = 0, ''
    
    while i < len(sequence):
        if sequence[i] in sequence[:i]:
            i -= 1
            sequence = sequence[1:]
        else:
            i += 1
            b = max(b, sequence[:i], key=len)

    return b

def longest_unique_sequence(sequence):
    i, j = 0, 0

    while j < len(sequence):
        if sequence[j] in sequence[i:j]:
            i += 1
        else:
            j += 1
            yield sequence[i:j]

def longest_unique_sequence(sequence):
    i, k = 0, {}

    for j, x in enumerate(sequence):
        i = max(i, k.get(x, 0))
        k[x] = j + 1
        yield sequence[i:j + 1]

def longest_unique_sequence(sequence, best=''):
    for x in sequence:
        best = best[best.find(x) + 1:] + x
        yield best