Is Ways to Split Array Into Good Subarrays easy or hard?

The problem is rated Medium because the implementation is simple but the key insight is not immediately obvious. Recognizing that zeros between consecutive 1s create multiple valid split points is the main step needed to derive the optimal O(n) solution.

Ways to Split Array Into Good Subarrays Python/Java solution

Most implementations follow the same pattern across languages: iterate through the array, track the previous index of 1, compute the gap when the next 1 appears, and multiply the answer by that gap size. Python, Java, and C++ implementations typically complete this in under 10 lines using simple loops.

How to solve Ways to Split Array Into Good Subarrays in O(n)?

Traverse the array and track the index of each 1. For every pair of consecutive 1s, compute the distance between them, which represents the number of valid split points. Multiply these values across all pairs. This single-pass approach yields an O(n) time solution with constant extra space.

What is the best approach for Ways to Split Array Into Good Subarrays?

The Gap Counting Method is the most efficient and commonly used solution. It counts the number of zeros between consecutive 1s and multiplies the possible split choices. If there are k zeros between two 1s, you get k+1 ways to place a boundary. This produces an O(n) time and O(1) space solution.

Is Ways to Split Array Into Good Subarrays asked at Google/Amazon/Meta?

Problems combining array traversal with combinatorial counting appear frequently in interviews at companies like Amazon, Google, and Meta. Variants often test whether candidates recognize patterns in binary arrays and convert them into simple mathematical counts.

What data structure is used in Ways to Split Array Into Good Subarrays?

The solution primarily uses basic array traversal with a few integer counters. No advanced data structures are required. The core idea relies on mathematical counting of gaps between elements in a binary array.

What is the time complexity of Ways to Split Array Into Good Subarrays?

The optimal solution runs in O(n) time because the array is scanned once to locate the positions of 1s and compute the gaps between them. Space complexity is O(1) since only a few counters and the previous index of 1 are stored.

Description Hints 3 Solution Video 6:50

2750. Ways to Split Array Into Good Subarrays

Medium34.9% acceptance1 company

You are given a binary array nums.

A subarray of an array is good if it contains exactly one element with the value 1.

Return an integer denoting the number of ways to split the array nums into good subarrays. As the number may be too large, return it modulo 10⁹ + 7.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

Input: nums = [0,1,0,0,1]
Output: 3
Explanation: There are 3 ways to split nums into good subarrays:
- [0,1] [0,0,1]
- [0,1,0] [0,1]
- [0,1,0,0] [1]

Example 2:

Input: nums = [0,1,0]
Output: 1
Explanation: There is 1 way to split nums into good subarrays:
- [0,1,0]

Constraints:

1 <= nums.length <= 10⁵
0 <= nums[i] <= 1

Asked at 1 company

Flipkart

Topics

Hints open one at a time

Hint 1

If the array consists of only 0s answer is 0.

Hint 2

In the final split, exactly one separation point exists between two consecutive 1s.

Hint 3

In how many ways can separation points be put?

6:50

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