10 Tower Research Capital Software Engineer (New Grad) Interview Questions (2026)

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STAR. Pick a real bug — segfault, leak, corruption, use-after-free. Walk through diagnosis (gdb, valgrind, sanitizers, strace, code review), the root cause, the fix, what you learned. Tower values systematic debugging — heroic guesses score lower than tool-assisted analysis.

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Specific reasons: multiple trading groups offering career flexibility, technology focus (low-latency systems), global presence (NY, London, Singapore, Mumbai), broad asset class exposure. Avoid 'high pay' as the lead. Reference Tower's specific group focus if you have one in mind (Latour for equity HFT, Spire-X for new strategies).

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Iterative: maintain prev=null, curr=head. Loop: next = curr.next; curr.next = prev; prev = curr; curr = next. Return prev. O(n) time, O(1) space. Walk through with example. Mention recursive alternative — recurse on rest, then point rest.next.next = current.

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2D DP. dp[t][i] = max profit using up to t transactions through day i. dp[t][i] = max(dp[t][i-1], max over j<i of prices[i] - prices[j] + dp[t-1][j-1]). Optimize inner max: track best (dp[t-1][j-1] - prices[j]) seen so far. O(k·n) time, O(k·n) space (or O(n) with rolling). Walk through the optimization.

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Array of linked lists (buckets). Hash function modulo array size. Insert: append to bucket's list (or skip if exists). Lookup: scan bucket's list. Delete: remove from bucket's list. Load factor > 0.75 → resize. Walk through; code cleanly. Discuss alternatives: open addressing (linear probing, quadratic, double hashing) with tradeoffs.

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Count character frequencies. A palindrome has at most one character with odd count (the middle one if length is odd). Count odd-frequency characters; return true if ≤ 1. O(n) time, O(k) space where k is alphabet. Walk through example.

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Stack: grows down from high addresses, fast allocation (just adjust SP), automatic cleanup at function return, limited size (~8MB default on Linux). Heap: grows up from break or via mmap, manual allocation (malloc/free or new/delete), can fragment, much larger. Lifetime: stack tied to function scope; heap until explicit free. Walk through a function call showing stack frame layout. Discuss why stack allocation is preferred for short-lived data in hot paths.

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volatile: tells compiler not to optimize away reads/writes (e.g., for memory-mapped I/O). Does NOT provide thread safety. atomic: provides thread safety with defined memory ordering (acquire, release, seq_cst). Use atomic for shared variables across threads; volatile is for hardware interfaces or signal handlers. Common bug: using volatile for thread synchronization — compiles but is broken on modern memory models.

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False sharing: two threads write to different variables that share a cache line. CPU coherence protocol invalidates the line on every write, even though the writes are independent — causes severe performance degradation. Avoid: padding (alignas(64) or alignas(std::hardware_destructive_interference_size)) to ensure variables don't share lines. Discuss this is critical in multi-threaded trading code where multiple threads touch hot counters.

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Components: (1) Ingestion: parse exchange feed (FIX, ITCH, custom protocol). (2) Order book data structure: sorted price levels (red-black tree or array per side). (3) Updates: add, modify, delete orders, maintain top-of-book. (4) Snapshots: periodic checkpoints for recovery. (5) Distribution: publish updates to consumers (risk, execution, analytics). Discuss tradeoffs: latency vs feature richness. Walk through an example update flow.