team-codebug · Sanjana023 · Nov 22, 2025 · Nov 22, 2025 · Nov 22, 2025 · Nov 22, 2025
diff --git a/README.md b/README.md
@@ -1,134 +1,52 @@
-# 🚀 Babua DSA Patterns Course 2025 – 90 Day Challenge (by CTO Bhaiya)
+# 🚀 DSA Patterns Course 2025 – 90-Day Challenge
 
-Welcome to the **DSA Patterns 2025** Course — a **90-day challenge** to master the **30 core coding patterns** used in FAANG and top product interviews.  
-Instead of solving 1000 random questions, you'll learn how to **think in patterns** — and solve any problem confidently.
+A structured 90-day preparation plan to master the 30 essential **DSA Patterns** used in top product-based company interviews.  
+This repository contains my daily progress, notes, solved questions, and reflections.
 
 ---
 
-## 🚀 Pre-requistes of Babua DSA Patterns Sheet 2025
-[Onboarding Sheet](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/ONBOARDING.md)
-
-
-## 🚀 Babua DSA Patterns Sheet 2025
-[Babua Sheet](https://docs.google.com/spreadsheets/d/1T3vPcwlWdMRMYSf8IxQCKb3gX7rGzDss-ZU-R4XFM14/edit?usp=sharing)
-
-## 🚀 Babua DSA Patterns Revision Sheet 2025
-[Babua DSA Patterns Sheet 2025](https://docs.google.com/spreadsheets/d/1RESAUKlHFjdCrEO9YDySoHaHnn_FMdrAgSV9NdZdVos/edit?usp=sharing)
-- Make a copy of this sheet to start using the DSA Revision sheet
-- 🧠 **Revise Each thing at least 4 times** - Use the revision sheet to practice theory and questions multiple times so that you don't forget
-
-## 📘 About the Course
+## 📘 Course Overview
 
 **Duration:** 90 Days  
-**Instructor:** CTO Bhaiya (NITKian)  
-**Language:** Java (main), Python (optional), Hindi explanations  
-**Daily Timing:** 5 PM IST on YouTube  
-
-Each pattern includes:
-- 🎥 **Theory Video** — Learn the logic and intuition behind the pattern  
-- 🧠 **Problem Set (15–20 LeetCode Questions)**  
-- 🗒️ **Notes & Solutions**
-
----
+**Focus:** DSA Pattern-Based Learning  
+**Language:** Java (primary)
 
-## 💡 Why Learn DSA by Patterns?
+Each day includes:
 
-✅ Covers 95% of all coding interview problems  
-✅ Learn faster by recognizing problem patterns  
-✅ Helps you revise logically, not by brute memorization  
-✅ Builds intuition and confidence for FAANG-level interviews  
+- Concept explanation
+- Pattern intuition
+- Problem set
+- Notes & practice questions
 
 ---
 
-## 📅 90-Day Progress Tracker
-
-Mark your progress by ticking ✅ each day.  
-Links will be updated as the series goes live!
+## 🎯 My Goals
 
-| Day | Topic / Pattern | 🎥 Video Link | 🗒️ Notes | ✅ Done |
-|-----|------------------|---------------|-----------|--------|
-| 0 | Complete DSA Patterns In 90 Days Course - Crack Coding Interviews in 3 Months - Day 0/90 - Intro | [Watch Now](https://www.youtube.com/watch?v=zvK49innOZY&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/0_Day) | ✅ |
-| 1 | Day 1/90 - ⚡ Two Pointers Theory - DSA Pattern #1 - DSA Pattern You Must Know! | [Watch Now](https://www.youtube.com/watch?v=Elnhh8cC2vM&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=2) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/1_Day) | ✅ |
-| X | Disclaimer: NO CONTROVERSY!!! | [Watch Now](https://www.youtube.com/watch?v=vJ2xa878E-M&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=3) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/we_need_to_talk.svg) | ✅ |
-| X | DSA Crash Course (Topic-Wise) + Onboarding SHEET + PATTERNS LIST | [Watch Now](https://www.youtube.com/watch?v=Xl0wuOqWWfQ&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=4) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/sheet.svg) | ✅ |
-| 2 | Day 2/90 - ⚡Master 5 Two Pointer Problems - Babua DSA Patterns - Crack Coding Interviews | [Watch Now](https://www.youtube.com/watch?v=Yi90cuHYyWQ&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=5) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/2_Day) | ✅ |
-| X | The ONLY DSA Sheet You’ll Ever Need in 2025 ⚡ - 30 Patterns + Problems Explained | [Watch Now](https://www.youtube.com/watch?v=4KRw2qdWTKM&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=6) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/Babua-DSA-Patterns-Questions.svg) | ✅ |
-| 3 | Day 3/90 🔥 Master Two Pointer Pattern - 5 LeetCode Problems Explained - Babua DSA Patterns 2025 | [Watch Now](https://www.youtube.com/watch?v=SP065oLnxGA&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=7) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/3_Day) | ✅ |
-| 4 | Day 4/90 🔥Three Popular Interview Questions Two Pointer Pattern - Babua DSA Patterns 2025 | [Watch Now](https://www.youtube.com/watch?v=pcj6S1KLxWc&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=8) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/4_Day) | ✅ |
-| 5 | Day 5/90 🔥Three Popular Interview Questions of Two Pointer Pattern - Babua DSA Patterns 2025 | [Watch Now](https://www.youtube.com/watch?v=jA74srakqvI&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=9) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/5_Day) | ✅ |
-| X | Complete DSA Patterns Course 2025 - Recap + Onboarding + Homework - Babua DSA Patterns Course | [Watch Now](https://www.youtube.com/watch?v=MwI_UZlnl6I&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=10) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/Recap%20%2B%20Homework.excalidraw.svg) | ✅ |
-| X | From NOBODY to NITK, IITM, Intuit, Adobe, CTO and finally CEO of my own Company - My Journey so far | [Watch Now](https://www.youtube.com/watch?v=vMndRzz1SRo&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=11) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/MY%20JOURNEY.svg) | ✅ |
-| 6 | Day 6/90 🔥 Solve Three Popular String Interview Questions with 1 Trick - Babua DSA Patterns 2025 | [Watch Now](https://www.youtube.com/watch?v=IW8gQ2u2O_I&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=12) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/6_Day) | ✅ |
-| 7 | Day 7/90 - ⚡ 🚀 Fast & Slow Pointers Explained - Crack Linked List Problems in O(n) - DSA Pattern #2 | [Watch Now](https://www.youtube.com/watch?v=FguUjuCzhj0&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=13) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/7_Day) | ✅ |
-| 8 | Day 8/90 - ⚡ 🚀 5 Popular Interview Questions Fast & Slow Pointers Pattern - DSA Pattern #2 | [Watch Now](https://www.youtube.com/watch?v=eIItwq8UTmU&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=14) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/8_Day) | ✅ |
-| X | The DSA Revolution has started - And "THEY" are not HAPPY | [Watch Now](https://www.youtube.com/watch?v=lkbQGa2tEYQ&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=15) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/blob/main/DSA%20Revolution%20Started.excalidraw.svg) | ✅ |
-| 9 | Day 9/90 - ⚡ 🚀 3 Popular Interview Questions Fast & Slow Pointers Pattern - DSA Pattern #2 | [Watch Now](https://www.youtube.com/watch?v=E85jp_rHivc&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=16) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/9_Day) | ✅ |
-| 10 | Day 10/90 - ⚡2130. Maximum Twin Sum of a Linked List - Fast & Slow Pointers Pattern - DSA Pattern #2 | [Watch Now](https://www.youtube.com/watch?v=t40HN4Rla30&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=17) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/10_Day) | ✅ |
-| 11 | Day 11/90 - ⚡457. Circular Array Loop - Fast & Slow Pointers Pattern - DSA Pattern #2 | [Watch Now](https://www.youtube.com/watch?v=nFZ1mysCZc0&list=PLVItHqpXY_DDFNeS6NUUoRsloyaPRdl1l&index=18) | [Notes](https://github.com/team-codebug/babua-dsa-patterns-course/tree/main/11_Day) | ✅ |
+- Build strong fundamental intuition of DSA patterns
+- Solve 300+ high-quality coding problems
+- Maintain a 90-day consistency streak
+- Prepare effectively for internship & placement interviews
 
 ---
 
-## 🏁 How to Track Progress
-
-1. **Fork this repo**  
-2. Replace ⬜ with ✅ as you finish each day  
-3. Post daily updates on **LinkedIn** with the hashtag **#DSAin90Days** and tag **@CTOBhaiya**  
-4. Keep your streak — and share your learning journey!  
-
----
-
-## 🧩 **LinkedIn Daily Progress Template (for Students)**
-
-> 📅 **Day [X] / 90 – DSA Patterns Challenge 2025**
->
-> ✅ **Today’s Pattern:** [Pattern Name — e.g., Sliding Window / Two Pointers]
-> 🎥 **Video:** [YouTube Link]
-> 🗒️ **Notes:** [Notes Link or GitHub Link]
->
-> 🧠 **What I learned today:**
->
-> * [Write 1–2 key insights — e.g., how the sliding window helps optimize brute force approaches, etc.]
-> * [Any “aha moment” or tricky question solved today]
->
-> 🔍 **Next Goal:** [Example: Practice all LeetCode questions from this pattern / Revise previous pattern tomorrow]
->
-> 💬 **Reflection:**
-> [Share your experience — was it easy, tough, interesting? Encourage others to join in!]
->
-> 🚀 **#DSAin90Days #DSAPatterns2025 #CTOBhaiya #FAANGPreparation #LeetCodePatterns #CodingInterviewPreparation #LearnCodeCrack #ThinkInPatterns**
->
-> 🙌 Learning under the guidance of **[@Anuj Kumar](https://www.linkedin.com/in/anuj-kumar-9a188968/)** – Thank you for making DSA feel simple and structured!
-
----
-
-### 🧠 Example Post
-
-> 📅 **Day 4 / 90 – DSA Patterns Challenge 2025**
->
-> ✅ **Pattern:** Two Pointers
-> 🎥 **Video:** [https://youtu.be/...](#)
-> 🗒️ **Notes:** [https://github.com/...](#)
->
-> 🧠 Learned how to solve *“Remove Nth Node from End of List”* and *“3Sum”* efficiently using the two-pointer pattern.
-> The biggest takeaway today — **simplify the logic by narrowing down the search space** instead of brute forcing!
->
-> 🔍 **Next Goal:** Move to Fast & Slow Pointer pattern tomorrow.
->
-> 🙌 Thanks **[@Anuj Kumar](https://www.linkedin.com/in/anuj-kumar-9a188968/)** for this amazing structure!
->
-> 🚀 #DSAin90Days #DSAPatterns2025 #FAANGPreparation #CTOBhaiya #LeetCodePatterns #CodingInterviewPreparation #ZeroToHeroDSA
-
----
-
-## 🌟 Connect & Learn
+## 📅 90-Day Progress Tracker
 
-- 📺 [YouTube Channel](https://www.youtube.com/@CodingwithCTOBhaiya)  
-- 💼 [LinkedIn](https://www.linkedin.com/in/anuj-kumar-9a188968/)  
-- 🌐 [Website](#)
+| Day | Topic / Pattern                  | Video                                                    | Status |
+| :-: | -------------------------------- | -------------------------------------------------------- | ------ |
+|  1  | Two Pointers – Theory            | [Link](https://youtu.be/Elnhh8cC2vM?si=OVrgsym_qKhpVgj4) | ✅     |
+|  2  | Two Pointers – Questions         | [Link](https://youtu.be/Yi90cuHYyWQ?si=BK3RJK2C4gYBk9BG) | ✅     |
+|  3  | Two Pointers – Questions         | [Link](https://youtu.be/SP065oLnxGA?si=3rQcrVhkDQQn2nqZ) | ✅     |
+|  4  | Two Pointers – Questions         | [Link](https://youtu.be/pcj6S1KLxWc?si=lpDF9O_Yw8Bv1HI5) | ✅     |
+|  5  | Two Pointers – Questions         | [Link](https://youtu.be/jA74srakqvI?si=ecv4UgGYbSyz7Tml) | ✅     |
+|  6  | Two Pointers – Questions         | [Link](https://youtu.be/IW8gQ2u2O_I?si=CEOpWgrmnhlVKU1l) | ✅     |
+|  7  | Fast & Slow Pointers – Theory    | [Link](https://youtu.be/FguUjuCzhj0?si=WF-FZUP6NwullPjW) | ✅     |
+|  8  | Fast & Slow Pointers – Questions | [Link](https://youtu.be/eIItwq8UTmU?si=l-owDQYThTpMbeCC) | ✅     |
+|  9  | Fast & Slow Pointers – Questions | [Link](https://youtu.be/E85jp_rHivc?si=ZPjAqpnRoUflGtfo) | ✅     |
+| 10  | Fast & Slow Pointers – Questions | [Link](https://youtu.be/t40HN4Rla30?si=FtncjOsYniEbYk9L) | ✅     |
+| 11  | Fast & Slow Pointers – Questions | [Link](https://youtu.be/nFZ1mysCZc0?si=orEJbkm8q9NEOdQb) | 🔲     |
 
 ---
 
-**Let’s master DSA by patterns — not by luck.**  
-Start your journey today. Comment “Done ✅” when you finish Day 0!  
+## 🔗 Resources
 
----
+- YouTube: _Coding with CTO Bhaiya_
diff --git a/my_solutions/Day_10 b/my_solutions/Day_10
@@ -0,0 +1,40 @@
+#LC 2130: Maximum Twin Sum of a Linked List
+(similar to palindrome LL)
+
+
+class Solution {
+    public ListNode findMid(ListNode head){
+        ListNode slow = head;
+        ListNode fast = head;
+        while(fast != null && fast.next != null){
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        return slow;
+    }
+    public int pairSum(ListNode head) {
+
+        ListNode midNode = findMid(head);
+
+        ListNode curr = midNode;
+        ListNode prev = null;
+        ListNode next;
+        while(curr != null){
+            next = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = next;
+        }
+        ListNode right = prev;
+        ListNode left = head;
+        int maxSum = Integer.MIN_VALUE;
+        int sum = 0;
+        while(right != null){
+            sum = left.val + right.val;
+            maxSum = Math.max(sum, maxSum);
+            left = left.next;
+            right = right.next;
+        }
+        return maxSum;
+    }
+}
diff --git a/my_solutions/Day_2 b/my_solutions/Day_2
@@ -0,0 +1,171 @@
+# 📝 Solutions
+
+#1️ Palindrome String  
+Problem: Check if a given string is a valid palindrome considering only alphanumeric characters and ignoring cases.
+
+# ✅ Solution
+
+class Solution {
+    public boolean isPalindrome(String s) {
+
+        int i = 0;
+        int j = s.length() - 1;
+
+        s = s.toLowerCase();
+
+        while(i < j)
+        {
+            char ch_i = s.charAt(i);
+            char ch_j = s.charAt(j);
+
+            if(!Character.isLetterOrDigit(ch_i)){
+                i++;
+                continue;
+            }
+
+            if(!Character.isLetterOrDigit(ch_j)){
+                j--;
+                continue;
+            }
+
+            if(ch_i != ch_j)
+                return false;
+
+            i++;
+            j--;
+        }
+        return true;
+    }
+}
+
+#️2 Reverse String
+Problem: Reverse the characters of a character array in-place.
+
+# ✅ Solution
+
+class Solution {
+    public void reverseString(char[] s) {
+        int i = 0;
+        int j = s.length - 1;
+
+        while(i < j){
+
+            char temp = s[i];
+            s[i] = s[j];
+            s[j] = temp;
+
+            i++;
+            j--;
+        }
+    }
+}
+
+
+#️3 Sorted Squares 
+Problem:Given a sorted array, return the array of squares of each number, sorted non-decreasing.
+
+# ✅ Solution
+
+class Solution {
+    public int[] sortedSquares(int[] nums) {
+
+        int i = 0;
+        int j = nums.length - 1;
+
+        int[] ans = new int[nums.length];
+        int idx = nums.length - 1;
+
+        while(i <= j){
+
+            if(Math.abs(nums[i]) > Math.abs(nums[j])){
+                ans[idx--] = nums[i] * nums[i];
+                i++;
+            }
+            else{ // equal case handled automatically
+                ans[idx--] = nums[j] * nums[j];
+                j--;
+            }
+        }
+        return ans;
+    }
+}
+
+#️4 Valid Palindrome II
+Problem:Given a string s, return true if the s can be palindrome after deleting at most one character from it.
+
+# ✅ Solution
+class Solution {
+    public boolean helper(int i, int j, String s){
+
+        while(i < j){
+            if(s.charAt(i) != s.charAt(j))
+            return false;
+
+            i++;
+            j--;
+        }
+        return true;
+
+    }
+    public boolean validPalindrome(String s) {
+
+        int i = 0 ;
+        int j = s.length() - 1;
+
+        while(i < j){
+
+            char left = s.charAt(i);
+            char right = s.charAt(j);
+
+            if(left != right){
+                return helper(i + 1, j, s) || helper(i, j - 1, s);
+            }
+
+            i++;
+            j--;
+        }
+        return true;
+    }
+}
+
+#️5 Valid Word Abbreviation(NeetCode)
+
+class Solution {
+    public boolean validWordAbbreviation(String word, String abbr) {
+        int i = 0, j = 0;
+        int n = word.length(), m = abbr.length();
+
+        while(i < n && j < m){
+
+            char abbr_chr = abbr.charAt(j);
+
+            // Case 1: Letter → must match
+            if(Character.isLetter(abbr_chr)){
+                if(word.charAt(i) != abbr_chr)
+                    return false;
+
+                i++;
+                j++;
+            }
+            else {
+                // Leading zero not allowed
+                if(abbr_chr == '0') return false;
+
+                int dig = 0;
+
+
+                while(j < m && Character.isDigit(abbr.charAt(j))){
+                    dig = dig * 10 + (abbr.charAt(j) - '0');
+                    j++;
+                }
+
+
+                i += dig;
+            }
+        }
+
+        return i == n && j == m;
+    }
+}
+
+