最长公共前缀

输入: ["flower","flow","flight"]
输出: "fl"

输入: ["dog","racecar","car"]
输出: ""
解释: 输入不存在公共前缀。

public static String longestCommonPrefix1(String[] strs) {
       StringBuilder builder = new StringBuilder();
       if (strs != null && strs.length > 0) {
           Arrays.sort(strs);
           char[] a = strs[0].toCharArray();
           char[] b = strs[strs.length - 1].toCharArray();

           for (int i = 0; i < a.length; i++) {
               if (b.length > i  && a[i] == b[i]) {
                   builder.append(a[i]);
               } else {
                   return builder.toString();
               }
           }
       }
       return builder.toString();
   }