Find the longest substring in alphabetical order

Question

I have this code that I found on another topic, but it sorts the substring by contiguous characters and not by alphabetical order. How do I correct it for alphabetical order

Answer 1

Try changing this:

        if len(set(substr)) != (end - start): # found duplicates or EOS
            break
        if (ord(max(sorted(substr))) - ord(min(sorted(substr))) + 1) == len(substr):

to this:

        if len(substr) != (end - start): # found duplicates or EOS
            break
        if sorted(substr) == list(substr):

That will display ccl for your example input string. The code is simpler because you're trying to solve a simpler problem :-)

Answer 2

Wow, some really impressing code snippets here... I want to add my solution, as I think it's quite clean:

s = 'cyqfjhcclkbxpbojgkar'

res = ''
tmp = ''

for i in range(len(s)):
    tmp += s[i]
    if len(tmp) > len(res):
        res = tmp
    if i > len(s)-2:
        break
    if s[i] > s[i+1]:
        tmp = ''

print("Longest substring in alphabetical order is: {}".format(res))

Answer 3

Use list and max function to reduce the code drastically.

actual_string = 'azcbobobegghakl'
strlist = []
i = 0
while i < len(actual_string)-1:
    substr = ''
    while actial_string[i + 1] > actual_string[i] :
        substr += actual_string[i]
        i += 1
        if i > len(actual_string)-2:
            break
    substr += actual-string[i]
    i += 1
    strlist.append(subst)
print(max(strlist, key=len))

Answer 4

In a recursive way, you can import count from itertools

Or define a same method:

def loops( I=0, S=1 ):
    n = I
    while True:
        yield n
        n += S

With this method, you can obtain the value of an endpoint, when you create any substring in your anallitic process.

Now looks the anallize method (based on spacegame issue and Mr. Tim Petters suggestion)

def anallize(inStr):
    # empty slice (maxStr) to implement
    # str native methods
    # in the anallize search execution
    maxStr = inStr[0:0]
    # loop to read the input string (inStr)
    for i in range(len(inStr)):
        # loop to sort and compare each new substring
        # the loop uses the loops method of past
        # I = sum of: 
        #     (i) current read index
        #     (len(maxStr)) current answer length
        #     and 1
        for o in loops(i + len(maxStr) + 1):
            # create a new substring (newStr)
            # the substring is taked:
            # from: index of read loop (i)
            # to:   index of sort and compare loop (o)
            newStr = inStr[i:o]

            if len(newStr) != (o - i):# detect and found duplicates
                break
            if sorted(newStr) == list(newStr):# compares if sorted string is equal to listed string
                # if success, the substring of sort and compare is assigned as answer
                maxStr = newStr
    # return the string recovered as longest substring
    return maxStr

Finally, for test or execution pourposes:

# for execution pourposes of the exercise:
s = "azcbobobegghakl"
print "Longest substring in alphabetical order is: " + anallize( s )

The great piece of this job started by: spacegame and attended by Mr. Tim Petters, is in the use of the native str methods and the reusability of the code.

The answer is:

Longest substring in alphabetical order is: ccl

Answer 5

s = 'cyqfjhcclkbxpbojgkar'
r = ''
c = ''
for char in s:
    if (c == ''):
        c = char
    elif (c[-1] <= char):
        c += char
    elif (c[-1] > char):
        if (len(r) < len(c)):
            r = c
            c = char
        else:
            c = char
if (len(c) > len(r)):
    r = c
print(r)

Answer 6

Without using a library, but using a function ord() which returns ascii value for a character. Assumption: input will be in lowercase, and no special characters are used

s = 'azcbobobegghakl'

longest = ''

for i in range(len(s)):
    temp_longest=s[i]

    for j in range(i+1,len(s)):

        if ord(s[i])<=ord(s[j]):
            temp_longest+=s[j]
            i+=1
        else:
            break

    if len(temp_longest)>len(longest):
        longest = temp_longest

print(longest)