Java String Compression Challenge - Two Pointers

100 Days of Coding Challenge – Day 18 📌 Problem: Is Subsequence 💻 Language: Java 🧠 Concept Used: Two Pointer Technique 🔍 Platform: LeetCode Today’s challenge was to determine whether a string s is a subsequence of another string t. A subsequence means the characters appear in the same order, but not necessarily consecutively. Approach: ✔ Use two pointers to traverse both strings ✔ If characters match, move both pointers ✔ Otherwise, move the pointer of the second string ✔ If all characters of s are matched, it is a valid subsequence ✔ Time Complexity: O(n) ✔ Space Complexity: O(1) This problem reinforced how powerful the two-pointer technique can be for efficient string traversal. 🔗 Problem Link: https://lnkd.in/g_43jvhm 🔗 Code: https://lnkd.in/gG_7d2BC #100DaysOfCode #Day18 #Java #DSA #LeetCode #TwoPointers #Strings #ProblemSolving #CodingJourney

100 Days of Coding Challenge – Day 30 📌 Problem: Find the Index of the First Occurrence in a String 💻 Language: Java 🧠 Concept Used: String Matching (Brute Force) 🔍 Platform: LeetCode Today’s challenge was to find the first occurrence of a substring (needle) in a given string (haystack). If not found, return -1. Example: Input: "sadbutsad", "sad" Output: 0 Approach: ✔ Traverse the string from index 0 to n - m ✔ Extract substring of length m at each position ✔ Compare it with the target string ✔ Return index immediately when match is found ✔ If no match → return -1 Time Complexity: O(n × m) Space Complexity: O(1) 🔗 Problem Link: https://lnkd.in/g2ktYFFS 🔗 Code: https://lnkd.in/gynFixSQ #100DaysOfCode #Day30 #Java #DSA #LeetCode #Strings #ProblemSolving #CodingJourney

100 Days of Coding Challenge – Day 20 📌 Problem: Remove Duplicates from Sorted Array 💻 Language: Java 🧠 Concept Used: Two Pointer Technique 🔍 Platform: LeetCode Today’s challenge was to remove duplicates from a sorted array in-place while keeping the relative order of elements the same. Approach: ✔ Use two pointers — one to traverse the array and another to track the position of unique elements ✔ Compare the current element with the previous one ✔ If they are different, place the element at the next unique position ✔ Time Complexity: O(n) ✔ Space Complexity: O(1) 🔗 Problem Link: https://lnkd.in/g83THPD6 🔗 Code: https://lnkd.in/gmrtpCRT #100DaysOfCode #Day20 #Java #DSA #LeetCode #TwoPointers #Arrays #ProblemSolving #CodingJourney

100 Days of Coding Challenge – Day 19 📌 Problem: Merge Sorted Array 💻 Language: Java 🧠 Concept Used: Array Manipulation + Sorting 🔍 Platform: LeetCode Today’s challenge was to merge two sorted arrays into a single sorted array. The result must be stored inside the first array (nums1). Approach: ✔ Copy elements from both arrays into a temporary array ✔ Place the combined elements back into nums1 ✔ Sort the final array to maintain non-decreasing order Time Complexity: O((m+n) log (m+n)) Space Complexity: O(m+n) 🔗 Problem Link: https://lnkd.in/gyFfUaiE 🔗 Code: https://lnkd.in/gA-MrnqG #100DaysOfCode #Day19 #Java #DSA #LeetCode #Arrays #ProblemSolving #CodingJourney

100 Days of Coding Challenge – Day 26 📌 Problem: Remove Duplicates from Sorted Array II 💻 Language: Java 🧠 Concept Used: Two Pointer Technique + Counting 🔍 Platform: LeetCode Today’s challenge was to remove duplicates from a sorted array in-place, but this time allowing at most two occurrences of each element. Approach: ✔ Traverse the array and track occurrences using a counter ✔ Allow elements to appear at most twice ✔ Use a pointer k to place valid elements in the correct position ✔ Skip elements when they exceed the allowed count Time Complexity: O(n) Space Complexity: O(1) 🔗 Problem Link: https://lnkd.in/gm2_CHbz 🔗 Code: https://lnkd.in/gKxuTbsG #100DaysOfCode #Day26 #Java #DSA #LeetCode #TwoPointers #Arrays #ProblemSolving #CodingJourney

100 Days of Coding Challenge – Day 23 📌 Problem: Longest Consecutive Sequence 💻 Language: Java 🧠 Concept Used: Sorting + Sequence Counting 🔍 Platform: LeetCode Today’s challenge was to find the length of the longest sequence of consecutive numbers in an unsorted array. The numbers do not need to be adjacent in the original array, but they must form a continuous sequence like 1,2,3,4. Example: Input: [100, 4, 200, 1, 3, 2] Output: 4 → Longest sequence: [1,2,3,4] Approach: ✔ First sort the array ✔ Traverse the array and check if the next number is consecutive ✔ Skip duplicates ✔ Track the longest streak using a counter Time Complexity: O(n log n) (due to sorting) Space Complexity: O(1) 🔗 Problem Link: https://lnkd.in/gguN6KnH 🔗 Code: https://lnkd.in/gyVFpsbg #100DaysOfCode #Day23 #Java #DSA #LeetCode #Arrays #ProblemSolving #CodingJourney

Problem Solved Today 💡 Today I solved a basic problem on Arrays, and it taught me something important. 📌 Problem: Find the largest element in an array 📌 Approach: Used a simple loop to compare elements 📌 Language: C / Java 👉 What I learned: Instead of jumping to complex solutions, sometimes simple logic works best. Coding is not about writing big code, it’s about clear thinking. Small steps every day = big improvement over time 🚀 #CodingJourney #ProblemSolving #Java #CProgramming #DataStructures #LearnToCode #FutureEngineer

100 Days of Coding Challenge – Day 21 📌 Problem: Word Pattern 💻 Language: Java 🧠 Concept Used: HashMap + String Mapping 🔍 Platform: LeetCode A valid pattern means there must be a one-to-one mapping (bijection) between characters in the pattern and words in the string. In other words: • Each pattern character maps to exactly one unique word • Each word maps to only one pattern character Example: pattern = "abba" s = "dog cat cat dog" → ✅ true Approach: ✔ Split the string into words using split(" ") ✔ Use a HashMap to map pattern characters to words ✔ Ensure no two characters map to the same word ✔ Verify consistency during traversal Time Complexity: O(n) Space Complexity: O(n) 🔗 Problem Link: https://lnkd.in/grDzg_82 🔗 Code: https://lnkd.in/gA9CCyc5 #100DaysOfCode #Day21 #Java #DSA #LeetCode #HashMap #Strings #ProblemSolving #CodingJourney

Day 21 of Programming – Strings in Java Today I explored some important String operations that are commonly used in programming and coding interviews. 🔹 Topics Covered: • Reverse a String • Check whether a String is a Palindrome • Count / Check Spaces in a String 💡 1️⃣ Reverse a String Reversing a string means printing the characters in the opposite order. Example: Input: hello Output: olleh This helps in understanding loops and string indexing. 💡 2️⃣ Palindrome String A palindrome is a word that reads the same forward and backward. Examples: madam, level, racecar Logic: Reverse the string and compare it with the original string. 💡 3️⃣ Checking Spaces in a String Sometimes we need to count how many spaces are present in a sentence. Example: Input: "Java is fun" Spaces Count = 2 This helps in text processing and validation tasks. #Java #Programming #Strings #CodingJourney #LearningToCode #Developers #SoftwareDevelopment

Day 61 of #100DaysOfLeetCode 💻✅ Solved #541. Reverse String II problem in Java. Approach: • Converted the string into a character array • Traversed the array in steps of 2k • For every segment, reversed the first k characters • Used two-pointer technique to perform in-place reversal • Math.min() to handle cases where remaining characters are less than k Performance: ✓ Runtime: 2 ms (Beats 16.04% submissions) ✓ Memory: 44.80 MB (Beats 73.53% submissions) Key Learning: ✓ Practiced handling strings with fixed pattern intervals ✓ Improved control over indexing and boundaries ✓ Strengthened in-place modification techniques Learning one problem every single day 🚀 #Java #LeetCode #DSA #Strings #TwoPointers #ProblemSolving #CodingJourney #100DaysOfCode