14 articles
Implement a LIFO stack using only queue operations. Learn both the single-queue rotation trick and the two-queue approach — a classic data-structure design problem that tests your understanding of LIFO vs FIFO at FAANG interviews.
Implement a FIFO queue using two stacks with amortized O(1) push and pop. The two-stack lazy-transfer trick is a FAANG interview staple that demonstrates deep understanding of amortized complexity and LIFO vs FIFO semantics.
Count ping requests within the last 3000ms using a FIFO queue that evicts expired timestamps from the front in O(1) amortized time. A clean introduction to the sliding window queue pattern used in rate limiters and real-time counters.
Find the minimum CPU intervals to execute all tasks with cooldown n using a greedy formula based on maximum frequency. A key FAANG problem testing greedy reasoning, frequency counting, and optionally heap-based simulation asked at Amazon, Google, and Facebook.
Solve LeetCode 994 Rotting Oranges step by step using multi-source BFS with a queue. A FAANG interview favorite at Amazon, Google, and Microsoft that teaches level-order traversal, simultaneous infection spread, and grid traversal patterns.
Solve LeetCode 207 Course Schedule using Kahn algorithm BFS topological sort with a queue and indegree array. A FAANG interview classic at Amazon, Google, and Meta that tests cycle detection in a directed graph.
Solve LeetCode 210 Course Schedule II by returning an actual topological order using Kahn algorithm BFS or DFS with three colors. A FAANG interview classic at Amazon, Google, Meta, and Microsoft.
Solve LeetCode 127 Word Ladder using BFS with a queue and a wildcard pattern map for O(1) neighbor lookups. A FAANG hard at Amazon, Google, Meta, and Microsoft that tests BFS on implicit graphs.
Solve LeetCode 622 Design Circular Queue with a fixed-size array and two pointers to achieve O(1) enQueue, deQueue, Front, and Rear. A FAANG interview classic at Amazon, Google, and Meta.
Solve LeetCode 417 Pacific Atlantic Water Flow with reverse BFS from both ocean borders using a deque queue. A FAANG grid traversal classic asked at Amazon, Google, and Meta.
Solve LeetCode 286 Walls and Gates with multi-source BFS from every gate using a deque queue in O(m times n). A FAANG grid traversal classic.
Solve LeetCode 362 Design Hit Counter using a queue or fixed-size circular buffer for O(1) amortized hits and constant-time getHits. A FAANG system design favorite.
Solve LeetCode 297 Serialize and Deserialize Binary Tree with a BFS queue producing a level-order encoding parsed in O(n). A FAANG hard tree design favorite.
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