13. Longest Substring Without Repeating Characters - Session Management

You're building a session management system that tracks user activity sequences. You need to find the longest sequence of unique activities without any repetition, which helps identify unique user behavior patterns and generate unique session IDs.

Given a string s, find the length of the longest substring without repeating characters.

Requirements

1. Basic Functionality

• Find longest substring with all unique characters
• Return the length of that substring
• Handle empty string (return 0)

Example Usage

lengthOfLongestSubstring("abcabcbb"); // 3 - "abc"
lengthOfLongestSubstring("bbbbb");    // 1 - "b"
lengthOfLongestSubstring("pwwkew");  // 3 - "wke"
lengthOfLongestSubstring("");        // 0

Real-World Context

This problem models real session management scenarios:

• Session tracking: Find longest unique activity sequence
• Unique ID generation: Generate IDs without repeating patterns
• Duplicate detection: Identify longest unique sequences in logs
• User behavior analysis: Track unique user interaction patterns