3

Longest Common Prefix

Difficulty: HARD
Contributed By
Srejan Kumar Bera
Avg. time to solve
40 min
Success Rate
60%

Problem Statement
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You are given an array ‘ARR’ consisting of ‘N’ strings. Your task is to find the longest common prefix among all these strings. If there is no common prefix, you have to return an empty string.

A prefix of a string can be defined as a substring obtained after removing some or all characters from the end of the string.

For Example:
Consider ARR = [“coding”, ”codezen”, ”codingninja”, ”coders”]
The longest common prefix among all the given strings is “cod” as it is present as a prefix in all strings. Hence, the answer is “cod”.
Input Format:
The first line of the input contains a single integer, 'T,’ denoting the number of test cases.

The first line of each test case contains a single integer ‘N’ denoting the number of strings in the array.

The next line contains ‘N’ space-separated strings denoting the elements of the array ‘ARR’.
Output Format:
For each test case, print a single string corresponding to the longest common prefix.

Print the output of each test case in a separate line.
Note:
You do not need to print anything. It has already been taken care of. Just implement the given function.
Constraints:
1 <= T <= 10
1 <= N <= 3000
1 <= |ARR[i]| <=1000

Each string consists of only lowercase letters.

Time limit: 1 sec
Sample Input 1:
2
4
coding codezen codingninja coder
3
night ninja nil 
Sample Output 1:
cod
ni
Explanation of sample input 1:
For the first test case, 
The longest common prefix among all the given strings is “cod” as it is present as a prefix in all strings. Hence, the answer is “cod”.

For the second test case,
The longest common prefix among all the given strings is “ni” as it is present as a prefix in all strings. Hence, the answer is “ni”.
Sample Input 2:
2
3
applejuice applepie apple
4
car cus cart carat
Sample Output 2:
apple
c
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