This code defines a function `longest_increasing_subsequence(nums)` that calculates the length...

April 3, 2025 at 02:14 PM

def longest_increasing_subsequence(nums):
    max_len = 0
    curr_len = 0
    subsequence = []
    temp_subseq = []
    for i in range(len(nums)):
        if i == 0 or nums[i] > nums[i-1]:
            curr_len += 1
            temp_subseq.append(nums[i])
        else:
            if curr_len > max_len:
                max_len = curr_len
                subsequence = temp_subseq[:]
            curr_len = 1
            temp_subseq = [nums[i]]
    if curr_len > max_len:
        max_len = curr_len
        subsequence = temp_subseq[:]
    return max_len, subsequence
nums = list(map(int, input("Enter the numbers separated by spaces: ").split()))
length, subsequence = longest_increasing_subsequence(nums)
print("Longest Increasing Subsequence Length:", length)
print("Longest Increasing Subsequence:", subsequence)

This code defines a function longest_increasing_subsequence(nums) that calculates the length and the elements of the longest contiguous increasing subsequence (not necessarily the strictly longest increasing subsequence; rather, a single continuous portion of the given list) in a given list of numbers, and then uses it to process user input. Here's how the code operates step-by-step:

What It Does

Inputs a List of Numbers:
- The user is prompted to input a space-separated sequence of integers, which is read, split into separate strings, converted into integers, and stored in the list nums.
Iterates Through the List to Find the Longest Increasing Subsequence:
- It initializes variables:
  - max_len for tracking the length of the longest increasing subsequence found so far.
  - curr_len for tracking the current length of a contiguous increasing subsequence being processed.
  - subsequence for storing the longest subsequence found so far.
  - temp_subseq for temporarily holding the current contiguous subsequence.
- The code iterates through the list nums and checks whether the current number is greater than the previous number (indicating an increasing sequence). If so:
  - It increments the curr_len and appends the current number to temp_subseq.
- If the current number is not increasing (or at the end of the list), it checks whether the length of the current contiguous subsequence (curr_len) is greater than the current maximum length (max_len). If so:
  - Updates max_len.
  - Copies the current sequence in temp_subseq to subsequence.
- Finally, it handles the case where the longest subsequence ends at the end of the list by performing a similar check once the loop is finished.
Outputs Results:
- The function returns the length of the longest increasing subsequence (max_len) and its elements (subsequence).
- These results are printed to the user.

Example Input & Output

Input:

Enter the numbers separated by spaces: 10 20 30 10 15 20 5 6

Output (Explanation):

The longest contiguous increasing subsequence is [10, 15, 20] (or [10, 20, 30] if it occurs earlier in the input sequence).
Output will look like this:

Longest Increasing Subsequence Length: 3
Longest Increasing Subsequence: [10, 20, 30]

Key Notes

This implementation identifies contiguous increasing subsequences, not the general longest increasing subsequence that may skip some values to increase the sequence size. For example, in the list [1, 3, 5, 2, 4, 3, 5], it would identify [1, 3, 5] instead of [1, 3, 4, 5].

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This code defines a function `longest_increasing_subsequence(nums)` that calculates the **length**...

What It Does

Example Input & Output

Key Notes

This code defines a function `longest_increasing_subsequence(nums)` that calculates the length...