🔢 #82 Remove Duplicates from Sorted List Remove all duplicates from a sorted linked list, keeping only distinct numbers. Use a dummy node, traverse & skip duplicates, link unique nodes. Input: 1->2->3->3->4->4->5 Output: 1->2->5 ✅ O(n) time, O(1) space. #LinkedList

🔢 #81 Search in Rotated Sorted Array Find a target in a sorted array rotated at a pivot. 🎯 Use modified binary search: check which half is sorted, then narrow search. Input: [4,5,6,7,0,1,2], target=0 → Output: 4 ✅ O(log n) time, O(1) space. #BinarySearch #LeetCodeMedium

🔢 #80 Remove Duplicates from Sorted Array Clean a sorted array so each element appears once! ✨ Use two pointers to overwrite duplicates in-place. Example: [1,1,2,2,3] → [1,2,3], length = 3 ✅ Time: O(n), Space: O(1) #RemoveDuplicates #TwoPointers #LeetCodeEasy

🔥 Networking Cheat Sheet — Hacker Edition 🔥 🧩 OSI & TCP/IP: instant recall 🌐 IPs: IPv4/IPv6 & private ranges 🔌 Ports: FTP, SSH, DNS, HTTPS, RDP ⚠️ 🛠️ Commands: ping,traceroute,netstat,nmap,curl,dig 💻 🛡️ Security: firewall, IDS/IPS, VPN 🔐 💀 Attacks & ⚡ Defenses

🔢 #79 Word Search Find if a word exists in a 2D board by moving up/down/left/right. 🧩 ⚡ DFS + Backtracking → mark visited, explore, unmark. 📦 Ex: board=[["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word="ABCCED" → true ✅ 📊 Time: O(NM4^L), Space: O(L) #dfs

🔢 #78 Subsets Generate the power set of an array 🎯 Using DFS + Backtracking, at each step you either include ✅ or exclude ❌ an element → every path = new subset 🌟 Ex: [1,2,3] → [], [1], [2], [3], [1,2], [1,3], [2,3], [1,2,3] ✅ ⏱ O(2^n·n) | 📦 O(n) #DFS #Backtracking

🔢 #77 Combinations Given n & k, return all k-number combinations from 1..n. ⚡ Use backtracking: build recursively, track current combo, add when size=k. 📦 Example: n=4, k=2 → [ [1,2],[1,3],[1,4],[2,3],[2,4],[3,4] ] #Combinations #Backtracking #LeetCodeMedium

📝 #76 Minimum Window Substring Find the smallest substring in s containing all chars of t. Use sliding window + char count array, expand right, shrink left to minimize. Ex: s='ADOBECODEBANC', t='ABC' → 'BANC' O(n+m) time, O(128) space #SlidingWindow #LeetCodeHard

🎨 #75 Sort Colors FAST! 🔥 Array of 0️⃣,1️⃣,2️⃣? Sort IN-PLACE like a boss! Use Dutch National Flag 3-pointer magic: push 0s front, 2s back, 1s chill in the middle. 💨 One pass | O(n) | O(1) #SortColors #LeetCode #CodingHacks #ArrayMagic

#74 Search 2D Matrix Matrix sorted row-wise & first of each row > last of prev. Find target ✅ ⚡ Trick: treat it as 1D → Binary Search! row=mid/n, col=mid%n ⏱ O(log(mn)) | 💾 O(1) #Search2DMatrix #BinarySearch #LeetCodeMedium #InterviewReady

#73 Set Matrix Zeroes 🟦 Given an m×n matrix, if an element = 0 → set its row & col to 0. ⚡ In-place, O(1) space: use 1st row/col as markers → mark, zero out, then fix 1st row/col. 📊 Time: O(mn) | Space: O(1) #SetMatrixZeroes #LeetCodeMedium #InterviewReady

✏️ #72 Edit Distance Find min ops to convert word1 → word2 using insert, delete, replace. DP: dp[i][j] = min steps for first i,j chars. If same: dp[i][j]=dp[i-1][j-1], else =1+min(insert,del,rep). Ex: horse→ros =3 ✅ ⏱ O(mn) 💾 O(mn) #EditDistance #DP #LeetCode

🛣️ #71 Simplify Path Simplify a Unix-style absolute path. / separates dirs, . = current, .. = parent. Remove extra slashes. Ex: "/home/"→"/home", "/a/./b/../../c/"→"/c" ✅ ⏱ O(n) | 📦 O(n) #SimplifyPath #StringParsing #LeetCodeMedium #UnixPaths #EdgeCases

🪜 #70 Climbing Stairs Count ways to climb n stairs taking 1 or 2 steps at a time. Classic Fibonacci problem. Ex: n=2→2 ✅, n=3→3 ✅ ⏱ O(n) | 📦 O(1) #ClimbingStairs #DP #Fibonacci #LeetCodeEasy #InterviewReady #MathAndSequences #EdgeCases

📐 #69 Sqrt(x) Compute the integer part of √x (truncate decimals) for non-negative x. Use binary search for efficiency and avoid overflow. Ex: x=4→2 ✅, x=8→2 ✅ ⏱ O(log x) | 📦 O(1) #Sqrtx #BinarySearch #LeetCodeEasy #MathAndBinary #EdgeCases

📝 #68 Text Justification Format words into lines of length maxWidth. ⚡ Spread spaces evenly, put extra left, last line left-aligned. Ex: ["This","is","an","example","of","text","justification."],16 → ["This is an","example of text","justification. "] ✅ ⏱O(n) 📦O(n)

💻 #67 Add Binary Add 2 binary strings a & b ➕ return sum in binary. ⚡ Only 0/1, handle carry & different lengths. ✅ "11"+"1"→"100" ✅ "1010"+"1011"→"10101" ⏱ O(max(n,m)) | 📦 O(max(n,m)) #AddBinary #BinaryMath #LeetCodeEasy #InterviewReady #CarryOver

✨➕ #66 Plus One ✨ Increment a number stored as an array of digits 🔢. ⚡ Handles carry (9→10), no leading zeros (except 0). ✅ [1,2,3]→[1,2,4] ✅ [4,3,2,1]→[4,3,2,2] ✅ [9]→[1,0] ⏱ O(n) | 📦 O(1) #PlusOne #ArrayMath #LeetCodeEasy #InterviewReady #EdgeCases

🔢 #65 Valid Number Check if a string is a valid number: int, decimal, or scientific (e/E), with optional +/-. Ex: "0"✅ "0.1"✅ "abc"❌ "1e10"✅ "e3"❌ 💡 Trim spaces, handle sign, split num & exponent, validate parts. ⏱ O(n), 🗂 O(1). #StringParsing #LeetCodeHard

🛤️ #64 Minimum Path Sum Find the min path sum in an m×n grid, moving only ⬇️ or ➡️. Ex: [[1,3,1],[1,5,1],[4,2,1]] → 7 ✅ (path: 1→3→1→1→1) 💡 DP trick: dp[i][j] = grid[i][j] + min(top,left) ⏱ O(mn), 🗂 O(mn)/O(n). #DynamicProgramming #LeetCodeMedium #InterviewReady