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 

class Solution {
    public String longestCommonPrefix(String[] strs) {
     if (strs.length == 1){
            return strs[0];
        }
        StringBuilder sb = new StringBuilder();
        if (strs.length>1) {
            int len = strs[0].length();
            for (int i = 0; i < len; i++) {
                char curr = strs[0].charAt(i);
                for (int j = 1; j < strs.length; j++) {
                    if (strs[j].length()<=i ||strs[j].charAt(i) != curr) {
                        return sb.toString();
                    }
                    if (strs[j].charAt(i) == curr && j == strs.length - 1) {
                        sb.append(curr);
                    }
                }
            }
        }
       return sb.toString();
    }
}