Date Range Generator

Problem Statement

This task involves creating a generator that yields a sequence of dates from a specified start date to an end date, inclusive. The important aspect here is the step parameter, which determines how many days to skip between each date. Each date in the sequence should adhere to the YYYY-MM-DD format. The implementation should be robust enough to accommodate different ranges and step sizes, ensuring that the boundaries (start and end dates) are respected and the output is within the given constraints.

Examples

Example 1

Input:

start = "2023-04-01", end = "2023-04-04", step = 1

Output:

["2023-04-01","2023-04-02","2023-04-03","2023-04-04"]

Explanation:

const g = dateRangeGenerator(start, end, step);
g.next().value // '2023-04-01'
g.next().value // '2023-04-02'
g.next().value // '2023-04-03'
g.next().value // '2023-04-04'

Example 2

Input:

start = "2023-04-10", end = "2023-04-20", step = 3

Output:

["2023-04-10","2023-04-13","2023-04-16","2023-04-19"]

Explanation:

const g = dateRangeGenerator(start, end, step);
g.next().value // '2023-04-10'
g.next().value // '2023-04-13'
g.next().value // '2023-04-16'
g.next().value // '2023-04-19'

Example 3

Input:

start = "2023-04-10", end = "2023-04-10", step = 1

Output:

["2023-04-10"]

Explanation:

const g = dateRangeGenerator(start, end, step);
g.next().value // '2023-04-10'

Constraints

• new Date(start) <= new Date(end)
• start and end dates are in the string format YYYY-MM-DD
• 0 <= The difference in days between the start date and the end date <= 1500
• 1 <= step <= 1000

Approach and Intuition

To solve this problem, understanding both the problem domain (dates) and the specific coding constructs (generators) is necessary. Let's break down the approach based on the provided examples and constraints:

1. Understanding Date Manipulation: The core operation involves advancing a date by a certain number of days (step). This requires a fundamental understanding of date operations in programming, which can often be tricky due to issues like leap years and month variations.

2. Generator Basics: Generators are used here because they allow for lazy evaluation, only computing each next date when needed. This is efficient in terms of memory and computation, especially valuable when the range of dates is large but only a few values are used.

3. Iterative Solution:

   • Start from the given start date.
   • Increment the date by step days until (or while) the current date is less than or equal to the end date.
   • Yield each computed date in the standard format YYYY-MM-DD.

4. Handling Edge Cases:

   • The smallest possible step is one day, which would mean returning consecutive dates.
   • If the start date is the same as the end date and step is 1, only a single date should be returned, as observed in Example 3.

5. Validation and Constraints:

   • Ensure that the start date is not later than the end date to comply with the constraint new Date(start) <= new Date(end).
   • The range of possible differences in days (up to 1500) and the range for the step size (1 to 1000) suggest the need for checking that the step does not overshoot the end date in a single increment.

By understanding and synthesizing these elements, the implementation can effectively leverage Python's datetime and generator capabilities to provide a clean and efficient solution to the problem.

Solutions

/**
 * @param {string} begin
 * @param {string} finish
 * @param {number} increment
 * @yields {string}
 */
var generateDateRange = function* (begin, finish, increment) {
    const from = new Date(begin);
    const to = new Date(finish);

    while (from <= to) {
        yield from.toISOString().split('T')[0].trim();
        from.setDate(from.getDate() + increment);
    }
};