Gourav Bakshi @GouravXDev

Finally wrapped up the GFG 160! What began as fun turned into an insightful journey where I picked up many new DSA patterns I hadn’t known before. Completing it really boosted my skills—and the GFG T-shirt feels like the perfect memento of the hard work. #gfg160 #geeksforgeeks

Day 160 ✅ | #GFG160DaysOfCoding 📌 Find 2 Unique Numbers (Others Twice) 🔹 XOR all → gives xor of 2 uniques 🔹 Extract rightmost set bit → partition array 🔹 XOR in groups → get both numbers ⏱ O(N) | 💾 O(1) #BitManipulation #XOR #Arrays #DSA #GeekStreak2025

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Day 159 ✅ | #GFG160DaysOfCoding 📌 Find Unique Number (All Others Twice) 🔹 XOR all elements → duplicates cancel out 🔹 Remaining = the unique number ⏱ O(N) | 💾 O(1) #BitMagic #XOR #Arrays #DSA #geekstreak2025

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Day 158 ✅ | #GFG160DaysOfCoding 📌 Missing Number in Array 🔹 XOR all numbers 1..N+1 🔹 XOR with array elements 🔹 Remaining value = missing number ⏱ O(N) | 💾 O(1) #BitMagic #XOR #Arrays #DSA #GeekStreak2025

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Day 157 ✅ | #GFG160DaysOfCoding 📌 Find Duplicate (1..N-1) ✨ XOR trick :- ans ^= i ^ arr[i]; All cancel out → leftover = duplicate ⏱ O(N) | 💾 O(1) #BitMagic #XOR #Arrays #DSA #GeekStreak2025

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Day 156 ✅ | #GFG160DaysOfCoding 📌 Maximum XOR of Two Numbers in Array 🔹 Build Trie of binary forms 🔹 Query each num for opposite bits → max XOR 🔹 Track best across all pairs ⏱ O(N·logM) | 💾 O(N·logM) #Trie #BitManipulation #XOR #DSA #GeekStreak2025

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Day 155 ✅ | #GFG160DaysOfCoding 📌 Implement Trie 🔹 Node → children[] + isLeaf 🔹 Ops: Insert | Search | Prefix ⏱ O(L) / op | 💾 O(ΣL) #Trie #PrefixTree #Strings #DSA #GeekStreak2025

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Day 154 ✅ | #GFG160DaysOfCoding 📌 Minimum Weight Cycle 🔹 Build adjacency list 🔹 For each edge (u,v):  • Temporarily remove it  • Find shortest path(u,v) via Dijkstra  • Cycle = path + edge weight 🔹 Track min cycle ⏱ O(E·(V+E)logV) | 💾 O(V+E) #Graph #DSA #geekstreak2025

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Day 153 ✅ | #GFG160DaysOfCoding 📌 Floyd–Warshall 🌐 🔹 Dist matrix given 🔹 Try each vertex as intermediate 🔹 Update shortest paths dp-style 🔹 Works with negative weights (no cycle) ⏱ O(V³) | 💾 O(1) #Graph #FloydWarshall #DSA #GeekStreak2025

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Day 152 ✅ | #GFG160DaysOfCoding 📌 Bellman-Ford Algorithm 🛣️ 🔹 Initialize distance array with ∞ 🔹 Relax all edges V-1 times 🔹 Extra pass → detect negative cycles 🔹 Returns shortest path or -1 if cycle ⏱ O(V·E) | 💾 O(V) #Graph #BellmanFord #DSA #GeekStreak2025

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Day 151 ✅ | #GFG160DaysOfCoding 📌 Alien Dictionary 👽 🔹 Build graph from given words 🔹 DFS + recursion stack for topo sort 🔹 Detect cycle → invalid dictionary 🔹 Reverse topo order → alien language ⏱ O(V+E) | 💾 O(V+E) #Graph #TopoSort #DFS #DSA #geekstreak2025

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Day 150 ✅ | #GFG160DaysOfCoding 📌 Clone Undirected Graph 🧩 🔹 BFS traversal with Queue 🔹 HashMap<Node,Copy> to track clones 🔹 For each neighbor: clone if not visited 🔹 Link neighbors in cloned graph ⏱ O(V+E) | 💾 O(V) #Graph #BFS #CloneGraph #DSA #GeekStreak2025

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Day 149 ✅ | #GFG160DaysOfCoding 📌 Flood Fill Algorithm 🎨 🔹 DFS from starting pixel 🔹 Replace only matching oldColor 🔹 Explore 4 dirs (up, down, left, right) 🔹 Stop if out of bounds / diff color ⏱ O(N×M) | 💾 O(N×M) #Graph #DFS #FloodFill #DSA #GeekStreak2025

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Day 148 ✅ | #GFG160DaysOfCoding 📌 Dijkstra’s Algorithm 🛣️ 🔹 Build adjacency list (u,v,wt) 🔹 Use Min-Heap (PQ) for shortest dist 🔹 Update dist[v] if smaller via u 🔹 Stops when all nodes visited ⏱ O((V+E) logV) | 💾 O(V+E) #Graph #ShortestPath #DSA #geekstreak2025

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Day 147 ✅ | #GFG160DaysOfCoding 📌 Min Cost to Connect Houses 🏠 🔹 Use Prim’s Algorithm (MST) 🔹 Manhattan distance as edge weight 🔹 Min-Heap picks smallest cost edge 🔹 Sum until all houses are connected ⏱ O(N² logN) | 💾 O(N²) #Graph #MST #Prim #DSA #geekstreak2025

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Day 146 ✅ | #gfg160DaysOfCoding 📌 Articulation Point (Tarjan’s Algo) 🔹 Build adj list 🔹 Track dt[] (discovery) & low[] (lowest reach) 🔹 Root with >1 child → articulation 🔹 Non-root: if low[child] ≥ dt[curr] → articulation ⏱ O(V+E) | 💾 O(V+E) #gfg160 #GeekStreak2025

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Day 145 ✅ | #GFG160DaysOfCoding 📌Bridge Edge in a Graph ➡️Removed edge (c,d) ➡️ DFS from c ➡️ if d not reached → bridge found. ⚙️ T.C: O(V+E) | 💾 S.C: O(V+E) #GFG160 #Graphs #DSA #GeekStreak2025

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Day 144 ✅ | #GFG160DaysOfCoding 📌 Detect Cycle in Directed Graph 🔹 Build adjacency list from edges[][]. 🔹 DFS with recursion stack rec[] 🔹 If a node is revisited in current path → cycle ⏱ O(V+E) | 💾 O(V+E) #Graph #CycleDetection #DFS #DSA #geekstreak2025

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Day 143 ✅ | #GFG160DaysOfCoding 📌 Topological Sort (DFS) 🔹 Build adjacency list (directed edges) 🔹 Run DFS → push nodes post-visit in stack 🔹 Reverse stack = topo order ⏱ O(V+E) | 💾 O(V+E) #Graph #DFS #TopoSort #DSA #geekstreak2025

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Day 142 ✅ | #GFG160DaysOfCoding 🌊 Count Islands 🏝️ 🔹 Grid of 'L' & 'W' 🔹 For each 'L' → DFS flood-fill (8 dirs) 🔹 Mark visited as 'W' 🔹 Each DFS = 1 island ⏱ O(R×C) | 💾 O(R×C) #DFS #Graph #DSA #GeekStreak2025

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