How to restrict the longest sequence of the same letter using python

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How can I determine the longest sequence of the same letter using python?

For example I use the following code to print a shuffled list with 3 conditions A,B and C

from random import shuffle
condition = ["A"]*20
condition_B = ["B"]*20
condition_C = ["C"]*20

condition.extend(condition_B)
condition.extend(condition_C)
shuffle(condition)
print(condition)

Now i want to make sure that the same condition does not happen more than three times in a row.

E.g., allowed: [A, B, C, A, B, B, C, C, C, A, B….] Not allowed: [A, A, B, B, B, B, C, A, B...] (because of four B’s in a row)

How can I solve this problem? Thank you in advance.

Maybe you should build the list sequentially, rather than shuffling:

result = []
for i in range(60):     # for each item in original list
  start = true          # we haven't found a suitable one yet
  if start or i>2:      # don't do checking unless 3 items in list
    while start or (
           c==shuf[-1] and     # is the chosen value
           c==shuf[-2] and     # the same as any of
           c==shuf[-3] ):      # the last 3 items?
      idx = random.randint(0,len(condition))  # chose a new one
      c = condition[idx]
      start = false            
  result.append(c)      # add to result
  del condition[i]      # remove from list

Warning! not tested - just conceptual...

Maximum consecutive repeating character in string, Given a string, the task is to find maximum consecutive repeating character in string. The outer loop considers current character, the inner loop counts occurrences of current character. Python 3 program to find the Python using Map function · Maximum number of characters between any two same character in a string  Given a String (may contain both letters and digits), write a Python program to find the longest consecutive letter and digit substring. Examples: This is the Naive or brute force approach to find the longest consecutive letter and digit substring. We take two string type variable longest_letter and longest_digit.

# Validate with this function it return false if more than three consecutive characters are same else True.


def isValidShuffle( test_condition):

    for i in range(len(test_condition)-4):
        if len(set(test_condition[ i:i+4])) == 1:
            # set size will be 1 all four consecutive chars are same
            return False
    return True

Simplest way to create shuffled sequence of A,B,C for which isValidShuffle will return True.

from random import shuffle

# condition list contains 20 A's 20 B's 20 C's

seq = ['A','B','C']
condition = []

for seq_i in range(20):
    shuffle(seq)
    condition += seq

print(condition) # at most two consecutive characters will be same 

print(isValidShuffle(condition))

-----------------------------------------------------------------------------

Output
['A', 'B', 'C', 'B', 'C', 'A', 'C', 'B', 'A', 'C', 'B', 'A', 'C', 'A', 'B', 'C', 'B', 'A', 'B', 'A', 'C', 'B', 'C', 'A', 'B', 'C', 'A', 'C', 'A', 'B', 'B', 'C', 'A', 'B', 'A', 'C', 'A', 'B', 'C', 'C', 'A', 'B', 'A', 'B', 'C', 'B', 'A', 'C', 'C', 'A', 'B', 'B', 'C', 'A', 'B', 'A', 'C', 'A', 'B', 'C']

............................................................................................................................................................... This is not imposing your restriction while creating shuffled sequence but keeps on trying until it find the sequence which meets your consecutive char restriction.

validshuffle = False 

condition = ['A']*20 + ['B']*20 + ['C']*20

while not validshuffle:

    shuffle(condition)

    if isValidShuffle(condition):
        validshuffle = True

print(condition)

-------------------------------------------------------------------------------
Output

try
try
['A', 'C', 'A', 'B', 'B', 'C', 'B', 'C', 'A', 'C', 'A', 'C', 'B', 'B', 'B', 'C', 'A', 'A', 'B', 'C', 'A', 'A', 'B', 'B', 'C', 'B', 'B', 'C', 'B', 'C', 'C', 'B', 'A', 'B', 'B', 'A', 'C', 'A', 'A', 'C', 'A', 'C', 'B', 'C', 'A', 'A', 'C', 'A', 'C', 'A', 'C', 'B', 'B', 'B', 'A', 'B', 'C', 'A', 'C', 'A']

SequenceMatcher in Python, SequenceMatcher is a class available in python module named “difflib”. It can be A human-friendly longest contiguous & junk-free sequence comparator find_longest_match( ) returns a triple containing the longest matching block in in the outer loop, we check for the occurrence of that character in string b using b2j. Input 1 1 1 1 0 0 0 Output None, None 0, 4 The reason is obvious: the longestSequence does not distinguish between longest sequence of zeroes and longest sequence of ones, so 0 0 0 is not considered long enough. Avoid globals; prefer returning values. There is no need to pass size; a list already knows its size.

If you just want to know, how long is the longest subsequence, you could do this. This is iterating over it the sequence and recording the length of the subsequences of the same character, saving it, getting the max for each subsequence, and then, getting the max of characters.

This is not exactly the problem you mention, but It could be useful.

from random import shuffle

sequence = ['A']*20 + ['B']*20 + ['C']*20 
sequences = {'A': [], 'B':[], 'C':[]}
shuffle(sequence)
current = sequence[0]
acc = 0
for elem in sequence:
    if elem == current:
        acc += 1
    else:
        sequences[current].append(acc)
        current = elem
        acc = 1
else:
    sequences[current].append(acc)
for key, seqs in sequences.items():
    sequences[key] = max(seqs)
print(max(sequences.items(), key=lambda i: i[1]))

Length of the longest sequence of repeating characters, "Given a string, return the length of the largest "block" in the string. A block is a run of adjacent chars that are the same." Required output: maxBlock("hoopla  Using the same function, we will compare original string will all its substrings. Then, first for loop compare all the substrings with all the other substrings till we find the longest repeating sequence. Storing the longest string in the variable lrs if the length of x is greater than lrs. Solution Python

Find longest word in a string: are any of these algorithms good , (I'm using Python but what I'm looking for is more of a pseudocode or a general algorithm). I'm struggling with the last word (or the last character). This problem is just the modification of Longest Common Subsequence problem. The idea is to find the LCS (str, str)where str is the input string with the restriction that when both the characters are same, they shouldn’t be on the same index in the two strings. Below is the implementation of the idea. // C++ program to find the longest repeating.

LeetCode – Longest Substring Without Repeating Characters (Java), how is solution two O(n^3)?. Zaga. So I came up with an O(n) solution in python, please help me  The block of lines is repeated once for each element of the sequence, so in this example the two lines in the indented block are repeated three times. Furthermore the variable in the heading ( count here) may be used in the block, and each time through it takes on the next value in the sequence, so the first time through the loop count is 1, then 2, and finally 3.

Python Basic (Part-II)- Exercises, Practice, Solution, Write a Python function that takes a sequence of numbers and determines whether all For this problem, we will limit ourselves to arithmetic progression whose The number of letters in the text is less than or equal to 1000. Difference between the largest and the smallest integer from the given integer: Set the two sequences to be compared. SequenceMatcher computes and caches detailed information about the second sequence, so if you want to compare one sequence against many sequences, use set_seq2() to set the commonly used sequence once and call set_seq1() repeatedly, once for each of the other sequences.

Comments
  • What have you tried so far? It is recommended you share your attempts so we can make recommendations based on it. Suffice to say in this case most likely a simple shuffle is not what you're looking for, you'll need to define your own shuffle function to apply the limitations.
  • Related / possible duplicate: How to randomize the order of elements of a list while making sure no consecutive values are equal?
  • What is the range of conditions and populations you're using? If it's merely three conditions with 20 of each, a brute-force solution is good; if you have larger populations, you might need a constructive approach.