算法：最长公共前缀字符串14. Longest Common Prefix

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题目

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"

Example 2:

Input: strs = ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

Constraints:

0 <= strs.length <= 200
0 <= strs[i].length <= 200
strs[i] consists of only lower-case English letters.

LCP水平扫描获取相邻最大共同前缀

LCP数组(Longest Common Prefix Array)：是由后缀数组中相邻两个后缀的最长公共前缀的长度组成的数组。

首先，我们将描述一种简单的方法来查找一组字符串共享的最长前缀.LCP(S1…Sn).
我们得出如下规律
LCP(S1…Sn)=LCP(LCP(LCP(S1,S2),S3),…Sn)

class Solution {
    public String longestCommonPrefix(String[] strs) {
        // check edge
        if (strs == null || strs.length == 0) {
            return "";
        }
        
        if (strs.length == 1) {
            return strs[0];
        }
        
        String preS = strs[0];
        for(int i = 1; i < strs.length; i++) {
            while(strs[i].indexOf(preS) != 0) {
                preS = preS.substring(0, preS.length() - 1);
                if (preS.isEmpty()) {
                    return "";
                }
            }
        }
        
        return preS;
    }
}