答案

public class Solution {
    int minLEN=Integer.MAX_VALUE;
    public String longestCommonPrefix(List<String>strs)
    {
        if(minLEN==0)
        {
            return "";
        }
        int LEN=strs.size();
        if(LEN==1)
        {
            return strs.get(0);
        }
        List<String >prefix=new LinkedList<String>();
        int index=0;
        StringBuilder builder=new StringBuilder("");
        for(index=1;index<LEN;index+=2){
            builder.delete(0,builder.length());
            String a=strs.get(index);
            String b=strs.get(index-1);
            minLEN=Math.min(a.length(),minLEN);
            minLEN=Math.min(b.length(),minLEN);
            for(int i=0;i<minLEN;i++){
                if(a.charAt(i)==b.charAt(i))
                {
                    builder.append(a.charAt(i));
                    continue;
                }
                break;
            }
            prefix.add(builder.toString());
        }
        if(index==LEN)
        {
            prefix.add(strs.get(index-1));
        }
        return longestCommonPrefix(prefix);
    }
    public String longestCommonPrefix(String[] strs) {
        if(strs==null||strs.length==0)
        {
            return "";
        }
        List<String>list=new LinkedList<String>();
        for(String s:strs)
        {
            list.add(s);
        }
        return longestCommonPrefix(list);
    }
}