Leetcode #2758: Next Day

In this guide, we solve Leetcode #2758 Next Day 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

Write code that enhances all date objects such that you can call the date.nextDay() method on any date object and it will return the next day in the format YYYY-MM-DD as a string. Example 1: Input: date = "2014-06-20" Output: "2014-06-21" Explanation: const date = new Date("2014-06-20"); date.nextDay(); // "2014-06-21" Example 2: Input: date = "2017-10-31" Output: "2017-11-01" Explanation: The day after 2017-10-31 is 2017-11-01.

Quick Facts

• Difficulty: Easy
• Premium: Yes
• Tags: JavaScript

Intuition

The constraints allow a direct scan that keeps only the essential state.

By translating the requirements into a clean loop, the logic stays easy to reason about.

Approach

Iterate through the data once, updating the state needed to compute the answer.

Return the final state after the traversal is complete.

Steps:

• Parse the input.
• Iterate and update state.
• Return the computed answer.

Example

Python Solution

Complexity

The time complexity is O(n). The space complexity is O(1) to O(n).

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.