Leetcode #1663: Smallest String With A Given Numeric Value
In this guide, we solve Leetcode #1663 Smallest String With A Given Numeric Value in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
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.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Greedy, String
Intuition
A locally optimal choice leads to a globally optimal result for this structure.
That means we can commit to decisions as we scan without backtracking.
Approach
Sort or preprocess if needed, then repeatedly take the best available local choice.
Maintain the minimal state necessary to validate the greedy decision.
Steps:
- Sort or preprocess as needed.
- Iterate and pick the best local option.
- Track the current solution.
Example
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.
Python Solution
class Solution:
def getSmallestString(self, n: int, k: int) -> str:
ans = ['a'] * n
i, d = n - 1, k - n
while d > 25:
ans[i] = 'z'
d -= 25
i -= 1
ans[i] = chr(ord(ans[i]) + d)
return ''.join(ans)
Complexity
The time complexity is , where is the length of the string. The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.