Is Find Maximum Number of Non Intersecting Substrings easy or hard?

This problem is generally classified as Medium difficulty. The challenge lies in recognizing that each character defines a dependency range and that valid substrings must include all occurrences of their characters. Once intervals are constructed correctly, the remaining step becomes a standard greedy interval selection problem.

Find Maximum Number of Non Intersecting Substrings Python/Java solution

Python and Java implementations typically compute two arrays for first and last character positions, then iterate through the string to expand valid intervals. Candidate intervals are validated and added to the result using greedy selection by end index. The overall implementation remains O(n) time and constant space.

How to solve Find Maximum Number of Non Intersecting Substrings in O(n)?

Store the first and last occurrence of each character. For every character's first position, attempt to build a minimal valid substring by expanding the right boundary whenever a character inside has a later last occurrence. If a character inside appears before the start index, discard the interval. Collect all valid intervals and greedily choose the earliest finishing ones to maximize the count.

What is the best approach for Find Maximum Number of Non Intersecting Substrings?

The optimal approach uses character range expansion with a greedy interval selection strategy. First compute the first and last occurrence of each character. Expand intervals to ensure every character inside the substring appears only within that interval. After generating valid intervals, sort by ending index and greedily choose non-overlapping substrings. This runs in O(n) time with constant extra space.

Is Find Maximum Number of Non Intersecting Substrings asked at Google/Amazon/Meta?

Problems involving interval construction, greedy scheduling, and string boundary expansion frequently appear in interviews at companies like Google, Amazon, and Meta. Variants test the ability to convert character frequency constraints into intervals and apply greedy selection. The pattern is closely related to interval scheduling and partition-label style problems.

What data structure is used in Find Maximum Number of Non Intersecting Substrings?

The solution primarily uses arrays or hash tables to store the first and last occurrence of characters. After computing these ranges, intervals are processed using greedy logic similar to interval scheduling. No complex structures are required beyond simple arrays and sorting.

What is the time complexity of Find Maximum Number of Non Intersecting Substrings?

The optimized solution runs in O(n) time where n is the length of the string. Each character is processed while expanding intervals and building candidate substrings, and the alphabet size (26) keeps preprocessing constant. Space complexity is O(1) because only fixed-size arrays for character positions are required.

Description Hints 4 Video 11:10

3557. Find Maximum Number of Non Intersecting Substrings

Medium31.1% acceptance1 company

You are given a string word.

Return the maximum number of non-intersecting substrings of word that are at least four characters long and start and end with the same letter.

Example 1:

Input: word = "abcdeafdef"

Output: 2

Explanation:

The two substrings are "abcdea" and "fdef".

Example 2:

Input: word = "bcdaaaab"

Output: 1

Explanation:

The only substring is "aaaa". Note that we cannot also choose "bcdaaaab" since it intersects with the other substring.

Constraints:

1 <= word.length <= 2 * 10⁵
word consists only of lowercase English letters.

Asked at 1 company

Bloomberg

Topics

Hints open one at a time

Hint 1

Can we solve the problem using Dynamic Programming?

Hint 2

For each character c, store all occurrence indices in order

Hint 3

At each position i, let j be the first index of word[i]; if i - j >= 3, we can form substring [j, i]

Hint 4

For each index, also store the maximum for any substring ending before that index in the dp.

LanguageLoading editor…

1class Solution:
2    def maxSubstrings(self, word: str) -> int:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

"abcdeafdef"

Input

"bcdaaaab"

Your code is saved on this device.