Is Maximum Score From Removing Substrings easy or hard?

Maximum Score From Removing Substrings is rated Medium difficulty on LeetCode. The implementation is straightforward once the greedy insight is recognized, but identifying that the higher scoring substring must be removed first is the key challenge.

Maximum Score From Removing Substrings Python/Java solution

Implement the greedy strategy: remove the higher-value substring first using a stack or counters, then process the remaining string for the other pair. The same logic works across Python, Java, C++, JavaScript, and C# with linear time complexity.

How to solve Maximum Score From Removing Substrings in O(n)?

Use a greedy strategy. Determine which substring ('ab' or 'ba') gives higher points and remove it first while scanning the string using a stack or counters. After finishing the first pass, process the remaining characters to remove the other substring type. This guarantees maximum score in linear time.

What is the best approach for Maximum Score From Removing Substrings?

The greedy approach with a stack is the most common solution. Always remove the higher scoring substring first ('ab' or 'ba'), then process the remaining string for the other pair. Each character is processed once, giving O(n) time complexity and O(n) space for the stack.

Is Maximum Score From Removing Substrings asked at Google/Amazon/Meta?

Greedy string manipulation and stack-based pattern removal problems frequently appear in interviews at companies like Amazon, Google, and Meta. This problem tests understanding of greedy ordering and efficient string processing in O(n) time.

What data structure is used in Maximum Score From Removing Substrings?

The most common solution uses a stack to track characters while scanning the string. The stack helps detect when the current character forms a removable pair with the previous one. An optimized approach can replace the stack with simple counters and two-pointer style scanning.

What is the time complexity of Maximum Score From Removing Substrings?

The optimal solution runs in O(n) time where n is the length of the string. Each character is pushed and popped from the stack at most once or processed once in the two-pointer version. Space complexity is O(n) with a stack or O(1) using the counting approach.

Description Hints 2 Solution Video 40:33

1717. Maximum Score From Removing Substrings

Medium66.6% acceptance7 companies

You are given a string s and two integers x and y. You can perform two types of operations any number of times.

Remove substring "ab" and gain x points.
- For example, when removing "ab" from "cabxbae" it becomes "cxbae".
Remove substring "ba" and gain y points.
- For example, when removing "ba" from "cabxbae" it becomes "cabxe".

Return the maximum points you can gain after applying the above operations on s.

Example 1:

Input: s = "cdbcbbaaabab", x = 4, y = 5
Output: 19
Explanation:
- Remove the "ba" underlined in "cdbcbbaaabab". Now, s = "cdbcbbaaab" and 5 points are added to the score.
- Remove the "ab" underlined in "cdbcbbaaab". Now, s = "cdbcbbaa" and 4 points are added to the score.
- Remove the "ba" underlined in "cdbcbbaa". Now, s = "cdbcba" and 5 points are added to the score.
- Remove the "ba" underlined in "cdbcba". Now, s = "cdbc" and 5 points are added to the score.
Total score = 5 + 4 + 5 + 5 = 19.

Example 2:

Input: s = "aabbaaxybbaabb", x = 5, y = 4
Output: 20

Constraints:

1 <= s.length <= 10⁵
1 <= x, y <= 10⁴
s consists of lowercase English letters.

Asked at 7 companies

Swiggy Juspay

Google Amazon Microsoft Meta Bloomberg

Topics

Hints open one at a time

Hint 1

Note that it is always more optimal to take one type of substring before another

Hint 2

You can use a stack to handle erasures

40:33

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