docs(revision): add algorithm descriptions for Day 02 string problems

Author: DeveloperViraj

CPP/revision/25-revision-questions/day-02-strings/01_longest_substring_without_repeating_characters.cpp

@@ -1,21 +1,20 @@
 // 01_longest_substring_without_repeating_characters.cpp
-// Problem: Longest Substring Without Repeating Characters
-// LeetCode: https://leetcode.com/problems/longest-substring-without-repeating-characters/
-// Author: DeveloperViraj (curated DSA set for Hacktoberfest 2025)
-// Compile: g++ -std=c++17 01_longest_substring_without_repeating_characters.cpp -o 01_longest_substring
-// Run: ./01_longest_substring
 //
-// Summary:
-// Given a string, find the length of the longest substring without repeating characters.
+// 🔍 Algorithm: Longest Substring Without Repeating Characters
+// Description:
+//   Finds the length of the longest substring in a given string 
+//   that contains no repeating characters.
+//   Uses the Sliding Window technique with a hash map to track 
+//   character indices and adjust window boundaries efficiently.
 //
-// Approach (sliding window + last-seen index):
-// Use two indices (windowStart and windowEnd) and a map of last-seen indices for characters.
-// Expand the windowEnd and if the current character was seen inside the current window,
-// move windowStart to lastSeenIndex + 1. Update the maximum window length as you go.
+// Use Case:
+//   Commonly used to analyze substring patterns or find unique 
+//   character sequences in data streams.
 //
-// Time Complexity: O(n) where n = length of string (each char visited at most twice).
-// Space Complexity: O(min(n, charset)) for the hash map of last seen indices.
-
+// Time Complexity: O(n) — each character visited once.
+// Space Complexity: O(1) — constant size (at most 256 chars).
+//
+// LeetCode: https://leetcode.com/problems/longest-substring-without-repeating-characters/
 #include <iostream>
 #include <string>
 #include <unordered_map>

CPP/revision/25-revision-questions/day-02-strings/02_minimum_window_substring.cpp

@@ -1,23 +1,21 @@
 // 02_minimum_window_substring.cpp
-// Problem: Minimum Window Substring
-// LeetCode: https://leetcode.com/problems/minimum-window-substring/
-// Author: DeveloperViraj (curated DSA set for Hacktoberfest 2025)
-// Compile: g++ -std=c++17 02_minimum_window_substring.cpp -o 02_minimum_window_substring
-// Run: ./02_minimum_window_substring
 //
-// Summary:
-// Given strings S and T, find the smallest substring in S that contains all characters of T
-// (including multiplicity). If no such window exists, return an empty string.
+// 🔍 Algorithm: Minimum Window Substring
+// Description:
+//   Finds the smallest substring in `source` that contains all 
+//   characters of `target` (including duplicates).
+//   Uses a Sliding Window approach combined with frequency maps 
+//   to expand and contract the window optimally.
+//
+// Use Case:
+//   Useful in text search problems, DNA sequence matching, 
+//   or when finding minimal segments containing specific data.
 //
-// Approach (sliding window + frequency maps):
-// 1. Build a frequency map for characters required by T.
-// 2. Expand 'right' pointer: add chars to current window counts.
-// 3. When the window satisfies all required counts (formed == required), try to shrink 'left'
-//    to minimize the window while still satisfying the requirement.
-// 4. Track best (smallest) window found during the process.
+// Time Complexity: O(|S| + |T|)
+// Space Complexity: O(|T|)
 //
-// Time Complexity: O(|S| + |T|) average (each char processed a constant number of times).
-// Space Complexity: O(CHARSET) or O(|T|) for maps.
+// LeetCode: https://leetcode.com/problems/minimum-window-substring/
+
 
 #include <iostream>
 #include <string>