Is Number of Ways to Separate Numbers easy or hard?

Number of Ways to Separate Numbers is classified as Hard on LeetCode. The difficulty comes from designing a DP state that enforces non‑decreasing numeric order while comparing substrings efficiently across many partitions.

Number of Ways to Separate Numbers Python/Java solution

Most implementations use a DP table plus an LCP preprocessing step. The algorithm works well in Python, Java, C++, and JavaScript because the complexity is O(n^2). The key is efficient substring comparison rather than language‑specific features.

How to solve Number of Ways to Separate Numbers in O(n^2)?

Use dynamic programming where dp[i][len] represents the number of valid ways ending at index i with a last number of length len. Precompute an LCP table so two substrings can be compared in constant time. This enables quick validation of the non‑decreasing constraint while iterating over candidate lengths.

What is the best approach for Number of Ways to Separate Numbers?

The optimal solution uses dynamic programming combined with fast substring comparison via an LCP (Longest Common Prefix) table. DP tracks how many valid sequences end at each position with a specific number length. LCP allows constant‑time lexicographic comparison between substrings, reducing the complexity to O(n^2) time and O(n^2) space.

Is Number of Ways to Separate Numbers asked at Google/Amazon/Meta?

Hard dynamic programming problems involving string comparison frequently appear in interviews at companies like Google, Amazon, and Meta. This specific problem tests DP state design, substring comparison optimization, and careful handling of constraints such as leading zeros.

What data structure is used in Number of Ways to Separate Numbers?

The core data structure is a dynamic programming table that tracks valid sequences by position and substring length. An auxiliary LCP table (related to suffix array concepts) is used for constant‑time substring comparison between candidate numbers.

What is the time complexity of Number of Ways to Separate Numbers?

The optimized dynamic programming solution runs in O(n^2) time with O(n^2) space. A preprocessing step builds an LCP table for substring comparison, which also costs O(n^2). Naive recursive solutions can reach O(n^3) or worse due to repeated substring comparisons.

Description Hints 2 Solution Video 44:19

1977. Number of Ways to Separate Numbers

Hard21.7% acceptance1 company

You wrote down many positive integers in a string called num. However, you realized that you forgot to add commas to seperate the different numbers. You remember that the list of integers was non-decreasing and that no integer had leading zeros.

Return the number of possible lists of integers that you could have written down to get the string num. Since the answer may be large, return it modulo 10⁹ + 7.

Example 1:

Input: num = "327"
Output: 2
Explanation: You could have written down the numbers:
3, 27
327

Example 2:

Input: num = "094"
Output: 0
Explanation: No numbers can have leading zeros and all numbers must be positive.

Example 3:

Input: num = "0"
Output: 0
Explanation: No numbers can have leading zeros and all numbers must be positive.

Constraints:

1 <= num.length <= 3500
num consists of digits '0' through '9'.

Asked at 1 company

Walmart Labs

Topics

Hints open one at a time

Hint 1

If we know the current number has d digits, how many digits can the previous number have?

Hint 2

Is there a quick way of calculating the number of possibilities for the previous number if we know that it must have less than or equal to d digits? Try to do some pre-processing.

44:19

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