Problem Statement
Character Rearrangement
You're working on a text formatting tool that needs to rearrange characters in a string to improve readability.
Given a string s, rearrange the characters of s so that any two adjacent characters are not the same.
Return any possible rearrangement of s or return an empty string if not possible.
Examples
Example 1:
Input: s = "aab"
Output: "aba"
Explanation: By rearranging the characters, we get 'aba'. This is a valid arrangement since no two adjacent characters are the same.
Example 2:
Input: s = "aaab"
Output: ""
Explanation: There is no way to rearrange the characters to avoid having two adjacent 'a's.
Constraints
- 1 <= s.length <= 500
- s consists of lowercase English letters.
Problem Breakdown
To solve this problem, we need to:
- If a character appears more than (n+1)/2 times (where n is the length of the string), it's impossible to rearrange the string to avoid adjacent duplicates
- The greedy approach of placing the most frequent characters first works well for this problem
- Alternating positions (even and odd indices) can be used to distribute characters evenly
- A priority queue (max heap) can efficiently track character frequencies and help with the greedy placement
- The problem can also be solved by constructing the result string character by character, always choosing the most frequent remaining character that is different from the last one used
String Problems
Learning Objective
Apply string manipulation concepts to solve a real-world problem.
Character Rearrangement
You're working on a text formatting tool that needs to rearrange characters in a string to improve readability.
Given a string s, rearrange the characters of s so that any two adjacent characters are not the same.
Return any possible rearrangement of s or return an empty string if not possible.
Examples
Example 1:
By rearranging the characters, we get 'aba'. This is a valid arrangement since no two adjacent characters are the same.
Example 2:
There is no way to rearrange the characters to avoid having two adjacent 'a's.
Problem Breakdown
Constraints:
- 1 <= s.length <= 500
- s consists of lowercase English letters.
Key Insights:
If a character appears more than (n+1)/2 times (where n is the length of the string), it's impossible to rearrange the string to avoid adjacent duplicates
The greedy approach of placing the most frequent characters first works well for this problem
Alternating positions (even and odd indices) can be used to distribute characters evenly
A priority queue (max heap) can efficiently track character frequencies and help with the greedy placement
The problem can also be solved by constructing the result string character by character, always choosing the most frequent remaining character that is different from the last one used
Real-World Application
This problem has several practical applications:
Text Formatting
Improving readability by avoiding repeated adjacent characters in text.
Data Compression
Rearranging data to optimize compression algorithms that work better with varied patterns.
Resource Scheduling
Scheduling tasks to avoid consecutive assignments of the same type.
Network Packet Distribution
Distributing network packets to avoid congestion from sequential similar packets.
Natural Language Processing
Generating text with better character distribution for improved readability.