Microsoft

The interviewer asked me to implement a memory-efficient spell checker that validates whether a word exists in a dictionary of 100 million entries; I walked through constructing a Compact Suffix Trie and a Bloom filter, comparing false-positive rates against bit-vector memory consumption, and concluded with a double-hashing scheme to minimize collision clustering. I was presented with a 2D map of scattered wireless sensor nodes where each node has an adjustable broadcast radius, and the interviewer asked me to determine the minimum transmission power required so that every node can reach every other node via multi-hop relay; I converted the problem into a bottleneck spanning tree by computing the minimum bottleneck edge over Euclidean distances using a modified Prim's algorithm with a priority queue. The interviewer framed an automated trading engine scenario where incoming buy and sell limit orders must be matched in real time based on price-time priority; I walked through designing an Order Book using a dual-level data structure combining a balanced binary search tree (or self-balancing skip list) for $O(\log P)$ price bucket navigation with doubly-linked lists inside each bucket to guarantee $O(1)$ order insertions, cancellations, and FIFO executions.