leetcode-14：Longest Common Prefix最长公共前缀

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: ["flower","flow","flight"] Output: "fl" Example 2: Input: ["dog","racecar","car"] Output: "" Explanation: There is no common prefix among the input strings. Note: All given inputs are in lowercase letters a-z.

编写一个函数来查找字符串数组中的最长公共前缀。 如果不存在公共前缀，返回空字符串 ""。 示例 1: 输入: ["flower","flow","flight"] 输出: "fl" 示例 2: 输入: ["dog","racecar","car"] 输出: "" 解释: 输入不存在公共前缀。 说明: 所有输入只包含小写字母 a-z 。

思路：先对字符串序列排序，排完后只需要比较第一个和最后一个字符串的前缀即可，若他俩相等其他肯定相等。还需注意字符串长度len应选择最短那个字符。

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if(strs.empty()) return "";
        sort(strs.begin(),strs.end());
        int i=0,len=min(strs[0].size(),strs.back().size());
        while(i<len && strs[0][i]==strs.back()[i]) i++;
        return strs[0].substr(0,i);
    }
};