Write a function to find the longest common prefix string amongst an array of strings.

解题思路：

老实遍历即可，注意边界条件：

JAVA实现：

static public String longestCommonPrefix(String[] strs) {          if (strs.length == 0)              return "";        for (int i = 0; i < strs[0].length(); i++) {              for (int j = 1; j < strs.length; j++)                  if (strs[j].length() == i || strs[j].charAt(i) != strs[0].charAt(i))                      return strs[0].substring(0, i);          }          return strs[0];      }

 C++：

1 class Solution { 2 public: 3     string longestCommonPrefix(vector
     
      & strs) { 4         if (strs.size() == 0) 5             return ""; 6         for (int i = 0; i < strs[0].length(); i++) { 7             for (int j = 1; j < strs.size(); j++) 8                 if (strs[j].length() == i || strs[j][i] != strs[0][i]) 9                     return strs[0].substr(0, i);10         }11         return strs[0];12     }13 };