Is Maximum Substrings With Distinct Start easy or hard?

Maximum Substrings With Distinct Start is generally classified as a medium difficulty problem. The brute force idea is straightforward, but recognizing that the next occurrence of the starting character defines the valid substring range requires deeper insight.

Maximum Substrings With Distinct Start Python/Java solution

Python and Java implementations typically store the next occurrence index in a map or array. After computing the next index for each character, iterate through the string and add nextIndex − i to the result. The logic is identical across Python, Java, C++, Go, and TypeScript.

How to solve Maximum Substrings With Distinct Start in O(n)?

Scan the string from right to left while maintaining a hash map of the latest index of each character. For position i, the next occurrence of s[i] determines the boundary where substrings stop being valid. The count of valid substrings starting at i equals nextIndex − i. Summing these values for all positions yields the final answer.

What is the best approach for Maximum Substrings With Distinct Start?

The optimal approach tracks the next occurrence of each character using a hash table. For every index i, determine where the same character appears next. All substrings ending before that index are valid. This allows counting valid substrings in O(n) time instead of checking each substring individually.

Is Maximum Substrings With Distinct Start asked at Google/Amazon/Meta?

String counting problems combined with hash tables frequently appear in interviews at companies like Amazon, Google, and Meta. Variants involving substring constraints, unique characters, and boundary calculations are especially common in medium‑level interview rounds.

What data structure is used in Maximum Substrings With Distinct Start?

A hash table (or dictionary) is used to store the most recent index of each character. This structure enables constant‑time lookup of the next occurrence of a character while scanning the string.

What is the time complexity of Maximum Substrings With Distinct Start?

The optimal solution runs in O(n) time where n is the length of the string. Each character is processed once while computing the next occurrence index using a hash table. Space complexity is O(n) for storing next positions or character indices.

Description Hints 1 Solution Video 7:12

3760. Maximum Substrings With Distinct Start

Medium90.4% acceptance

You are given a string s consisting of lowercase English letters.

Return an integer denoting the maximum number of substrings you can split s into such that each substring starts with a distinct character (i.e., no two substrings start with the same character).

Example 1:

Input: s = "abab"

Output: 2

Explanation:

Split "abab" into "a" and "bab".
Each substring starts with a distinct character i.e 'a' and 'b'. Thus, the answer is 2.

Example 2:

Input: s = "abcd"

Output: 4

Explanation:

Split "abcd" into "a", "b", "c", and "d".
Each substring starts with a distinct character. Thus, the answer is 4.

Example 3:

Input: s = "aaaa"

Output: 1

Explanation:

All characters in "aaaa" are 'a'.
Only one substring can start with 'a'. Thus, the answer is 1.

Constraints:

1 <= s.length <= 10⁵
s consists of lowercase English letters.

Topics

Hash Table String

Hints open one at a time

Hint 1

Count the number of distinct characters in s

7:12

Still stuck?Read the written solution, or watch a walkthrough.

Open solution

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1class Solution:
2    def maxDistinct(self, s: str) -> int:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2Case 3

Input

"abab"

Input

"abcd"

Input

"aaaa"

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