Introduction

In this blog post, we will explore how to solve the LeetCode problem "2522" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given a string s consisting of digits from 1 to 9 and an integer k. A partition of a string s is called good if: Each digit of s is part of exactly one substring. The value of each substring is less than or equal to k. Return the minimum number of substrings in a good partition of s. If no good partition of s exists, return -1. Note that: The value of a string is its result when interpreted as an integer. For example, the value of "123" is 123 and the value of "1" is 1. A substring is a contiguous sequence of characters within a string. Example 1: Input: s = "165462", k = 60 Output: 4 Explanation: We can partition the string into substrings "16", "54", "6", and "2". Each substring has a value less than or equal to k = 60. It can be shown that we cannot partition the string into less than 4 substrings. Example 2: Input: s = "238182", k = 5 Output: -1 Explanation: There is no good partition for this string. Constraints: 1 <= s.length <= 105 s[i] is a digit from '1' to '9'. 1 <= k <= 109

Explanation

Here's the solution to the problem:

• Greedy Approach: Iterate through the string from left to right. At each position, try to extend the current substring as much as possible while ensuring its value remains less than or equal to k.
• Partition Count: Increment the partition count each time a valid substring is formed.

• Invalid Partition: If at any position, even a single-digit substring exceeds k, a valid partition is not possible.

• Runtime Complexity: O(n), where n is the length of the string s. Storage Complexity: O(1).

Code

    def min_partitions(s: str, k: int) -> int:
    """
    Finds the minimum number of substrings in a good partition of s.

    Args:
        s: The string consisting of digits from 1 to 9.
        k: The maximum value of each substring.

    Returns:
        The minimum number of substrings in a good partition of s.
        Returns -1 if no good partition of s exists.
    """

    n = len(s)
    partitions = 0
    i = 0
    while i < n:
        current_num = 0
        j = i
        while j < n:
            current_num = current_num * 10 + int(s[j])
            if current_num > k:
                break
            j += 1

        if j == i:
            return -1  # Single digit exceeds k

        partitions += 1
        i = j

    return partitions