Introduction

In this blog post, we will explore how to solve the LeetCode problem "1663" 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

The numeric value of a lowercase character is defined as its position (1-indexed) in the alphabet, so the numeric value of a is 1, the numeric value of b is 2, the numeric value of c is 3, and so on. The numeric value of a string consisting of lowercase characters is defined as the sum of its characters' numeric values. For example, the numeric value of the string "abe" is equal to 1 + 2 + 5 = 8. You are given two integers n and k. Return the lexicographically smallest string with length equal to n and numeric value equal to k. Note that a string x is lexicographically smaller than string y if x comes before y in dictionary order, that is, either x is a prefix of y, or if i is the first position such that x[i] != y[i], then x[i] comes before y[i] in alphabetic order. Example 1: Input: n = 3, k = 27 Output: "aay" Explanation: The numeric value of the string is 1 + 1 + 25 = 27, and it is the smallest string with such a value and length equal to 3. Example 2: Input: n = 5, k = 73 Output: "aaszz" Constraints: 1 <= n <= 105 n <= k <= 26 * n

Explanation

Here's the breakdown of the solution:

• Greedy Approach: Start by filling the string with the smallest character 'a' as much as possible.
• Work from Right to Left: Fill the string from the right end. For each position, determine the largest character that can fit without exceeding the target numeric value k.

• Lexicographical Minimization: By filling from right to left with the largest possible character at each step, we ensure the lexicographically smallest string.

• Runtime Complexity: O(n) & Storage Complexity: O(n)

Code

    def getSmallestString(n: int, k: int) -> str:
    """
    Given two integers n and k, return the lexicographically smallest string with length equal to n and numeric value equal to k.
    """
    result = ['a'] * n
    k -= n  # Subtract the initial value of all 'a's

    for i in range(n - 1, -1, -1):
        add = min(k, 25)  # Determine the maximum possible addition to the current position
        result[i] = chr(ord('a') + add)  # Update the current position
        k -= add  # Update the remaining value to be filled

    return "".join(result)