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Search in Rotated Sorted Array at Meta — Interview Guide

How to approach Search in Rotated Sorted Array in a Meta interview: the optimal approach, what Meta interviewers look for, and company-specific tips.

Updated 2026-09MediumBinary Search

The problem at Meta

Search for a target value in an array that was sorted then rotated at an unknown pivot, in O(log n) time.

Meta uses this problem to assess move fast, ship impact, scale thinking. Expect Meta-specific follow-ups that tie the solution back to production reasoning and the company's engineering bar.

Key concepts

At each mid, one half is always sorted; identify it by comparing nums[mid] with nums[left].
If the target lies in the sorted half, search there; otherwise search the other half.
Handle duplicates carefully — when nums[left] == nums[mid] you cannot tell which side is sorted.

Approach

def search(nums, target):
    l, r = 0, len(nums) - 1
    while l <= r:
        m = (l + r) // 2
        if nums[m] == target: return m
        if nums[l] <= nums[m]:
            if nums[l] <= target < nums[m]: r = m - 1
            else: l = m + 1
        else:
            if nums[m] < target <= nums[r]: l = m + 1
            else: r = m - 1
    return -1

What Meta looks for

Coding speed and correctness — produce working, optimal code quickly.
Scale thinking — design for billions of users in the system design round.
Builder mindset — bias toward shipping and measuring.
Behavioral: impact, collaboration, and handling ambiguity.

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