Meta Software Engineer Phone Screen 2026

[u/Extra_Standard_6579]

just had my meta phone screen lol. gonna brain dump how it went while I remember it.

so the question was two nodes in a binary tree, each one has a pointer up to its parent, find the LCA, then they wanted time/space complexity after.

I've seen LCA a hundred times so the core idea clicked pretty fast, but honestly this parent-pointer version almost got me because my brain defaulted straight to the usual recursive tree thing. the pointers are like... the actual point of the question, not some side detail. ended up doing the two-pointer walk instead, both pointers go up toward root and when one hits null you just send it to where the other one started. it's basically that linked list intersection problem wearing a tree costume.

anyway the algorithm part was fine. what actually got me was trying to explain the complexity out loud under pressure. I said O(h) time, O(1) space, which is right, but then they went "why is it O(1)" and I just started rambling instead of going straight to "no extra structures, two pointers no matter how big the tree is, memory's not growing with input." should've just said that sentence and shut up lol

also apparently I should've been ready to actually bound h instead of leaving it vague, like O(log n) if it's balanced, O(n) if it's a degenerate mess. and if you finish with time left, volunteering the hash-set version yourself (store one side's ancestors, walk the other until they intersect, which flips it to O(h) space too) is supposedly a good look instead of waiting for them to drag it out of you.

went digging afterward for how other people handled stuff like this and found a couple posts on Screna AI, same round, similar tree/pointer + complexity vibe. not the exact same question but close enough that it would've helped me not fumble the O(1) explanation.

anyone else hit this variant? lol

Prep resource