JavaMediumStrings20 min
Find the longest common prefix
Print the longest prefix shared by all words, or an empty line if n=0 or no prefix exists. Follow the stated ordering and edge-case conventions exactly. Interviewers use this task to probe boundary handling and collection selection.
Input
n followed by n nonempty lowercase words separated by whitespace.
Output
Print the longest prefix shared by all words, or an empty line if n=0 or no prefix exists.
Constraints
0 <= n <= 10000; total word length <= 100000.
Example
Input
3 flower flow flight
Output
fl
Example 2 input
2 a ab
Output
a
This example exercises a further boundary or ordering case.
Public test cases (2)
Input
3 flower flow flight
Expected output
fl
Input
3 dog racecar car
Expected output
—
Hints (2)
- Identify the state needed to avoid recomputing work for each element.
- Maintain a prefix length and shorten it only when a later word disagrees.
Target complexity: time O(total input length) · space O(maximum word length)