Longest Common Prefix

Moderate

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65 upvotes

Problem statement

You are given an array ‘arr’ of ‘n’ strings.

Find the longest common prefix in all these strings.

If there is no common prefix in all the strings return "-1".

Example:

Input: 'arr' = [“abcd”, “abc”, “abref”, “abcde”]

Output: ab

Explanation:
Answer is “ab”, as it is the longest prefix present in all the given strings.

Detailed explanation ( Input/output format, Notes, Images )

Input format:

The first line contains an integer ‘n’, denoting the number of strings.

The next ‘n’ lines each contain a string, elements of array ‘arr’.

Output Format:

Return the longest common prefix of all the strings. If there is no such prefix, return “-1”.

Note:

You don’t need to print anything, it has already been taken care of, just complete the given function.

Sample Input 1:

4
Codingninjas
Coding
Coders
Codezen

Sample Output 1:

Cod

Explanation of sample output 1:

In the given testcase, the longest prefix that is present in all the strings is “Cod”. Hence the answer is “Cod”.

Sample Input 2:

3
abcd
Abcd
abc

Sample Output 2:

-1

Explanation of sample output 2:

In the given testcase, there is no prefix that is present in all the strings. Hence the answer is “-1”

Constraints:

1 <= ‘n’ <= 10^3
1 <= ‘arr[i].length’ <= 10^3

Time Limit: 1 sec

Expected Time Complexity:

Try solving this in O(n).

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