Longest Common Prefix
Write a function to find the longest common prefix string amongst an array of strings.
If there is no common prefix, return an empty string "".
Example 1:
Input: strs = ["flower","flow","flight"]
Output: "fl"
Explanation: "fl" is the longest common prefix shared by all three strings.
Example 2:
Input: strs = ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.
Example 3:
Input: strs = ["interspecies","interstellar","interstate"]
Output: "inters"
Explanation: "inters" is the longest prefix common to all three strings.
Examples
Example 1
Input: strs = ["flower","flow","flight"]
Output: "fl"
Explanation: All three strings start with "fl". The third string diverges at index 2 ('i' vs 'o'), so the longest common prefix is "fl".
Example 2
Input: strs = ["dog","racecar","car"]
Output: ""
Explanation: There is no character that all three strings share at index 0 ('d' vs 'r' vs 'c'), so the common prefix is empty.
Constraints
- -1 <= strs.length <= 200
- -0 <= strs[i].length <= 200
- -strs[i] consists of only lowercase English letters.
Optimal Complexity
Time
O(n * m)
Space
O(1)
Practice this problem with an AI interviewer
TechInView conducts a full voice mock interview — the AI asks clarifying questions, evaluates your approach, watches you code, and scores you on 5 dimensions. Just like a real FAANG interview.
Start a free interview