Python Challenges: Find the starting number, under ten thousand will create the longest chain

Last update on December 21 2024 07:49:41 (UTC/GMT +8 hours)

Write a Python program to find the starting number, under ten thousand will create the longest chain.

From Wikipedia - The Collatz conjecture is a conjecture in mathematics that concerns a sequence defined as follows: start with any positive integer n. Then each term is obtained from the previous term as follows: if the previous term is even, the next term is one half the previous term. If the previous term is odd, the next term is 3 times the previous term plus 1. The conjecture is that no matter what value of n, the sequence will always reach 1.

Sample Solution:

Python Code:

def create_sequence_num(n):
    terms = 1
    while n > 1:
        if n % 2 == 0:
            n = n / 2
        else:
            n = 3 * n + 1
        terms += 1
    return terms


def Collatz_starting_num():
    temp = 0
    i = 1
    while i < 10000:
        s = create_sequence_num(i)
        if s > temp:
            temp = s
            value = i
        i += 1

    return value

print(Collatz_starting_num())

Sample Output:

6171

Flowchart:

Python Code Editor:

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