Longest Common Prefix

Given the array of strings A, you need to find the longest string S which is the prefix of ALL the strings in the array.

Longest common prefix for a pair of strings S1 and S2 is the longest string S which is the prefix of both S1 and S2.

For Example: longest common prefix of "abcdefgh" and "abcefgh" is "abc".

0 <= sum of length of all strings <= 1000000

The only argument given is an array of strings A.

Return the longest common prefix of all strings in A.

Input 1:

A = ["abcdefgh", "aefghijk", "abcefgh"]

Input 2:

A = ["abab", "ab", "abcd"];

Output 1:

"a"

Output 2:

"ab"

Explanation 1:

Longest common prefix of all the strings is "a".

Explanation 2:

Longest common prefix of all the strings is "ab".