# Description

Given k strings, find the longest common prefix (LCP).

# Example

Example 1:

Input:

K strings = ["ABCD", "ABEF", "ACEF"]

Output:

"A"

Explanation:

The longest common prefix is "A".

Example 2:

Input:

K strings = ["ABCDEFG", "ABCEFG", "ABCEFA"]

Output:

"ABC"

Explanation:

The longest common prefix is "ABC".

# Code

1. if string length is 0 or string is null, then return "";
2. initialize prefix = strs[0] ;
3. traverse the strs[] , and compare the string with the prefix , if the char is the same is prefix, then j++
   • j should be the end index of the prefix
4. if j==0 meaning that there is one string doesn't have the same prefix as other, you can return "";

public class Solution {

    public String longestCommonPrefix(String[] strs) {

        if (strs.length == 0 || strs == null) return "";

        String prefix = strs[0];

        for (int i = 0; i < strs.length; i++) {

            int j = 0;

            while (j < prefix.length() && j < strs[i].length() && strs[i].charAt(j) == prefix.charAt(j)) {

                j++;

            }

            // 只要在 string [] 裡有一個 string 是不同 prefix, 都是錯

            if (j == 0) return "";

            // 都有一樣的 prefix, 那就取長度

            prefix = prefix.substring(0, j);

        }

        return prefix;

    }

}