Implement an algorithm to find the longest common prefix among an array of strings.

Why Prefix Matters in Data Engineering: Common in key design (e.g., S3 prefix for partitioning), schema evolution (shared column prefixes), and deduplication logic.

Scalability Trade-offs: (1) Horizontal scanning: O(S) where S = total chars—optimal for small-to-medium. (2) Vertical scanning: stops early on first mismatch—better when strings diverge quickly. (3) Sort-and-compare: O(n log n * m)—avoids full scan but sort dominates for large n. (4) Trie: O(S) build, O(m) query—when you have many prefix queries over same set.

Cost: At Hotstar-scale, prefix logic on millions of event keys—use Spark's reduceByKey with a custom prefix reducer; avoid collect() of all strings.

def longest_common_prefix(strs):
if not strs: return ''
prefix = strs[0]
for s in strs[1:]:
while not s.startswith(prefix):
prefix = prefix[:-1]
if not prefix: return ''
return prefix