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

Example:

Given ["abc","ab","abcd"],


return "ab".

class Solution {
    public String longestCommonPrefix(String[] strs) {
        String common = "";
        if(strs.length == 0)
            return "";
        else if(strs.length == 1)
            return strs[0];
        else{
            common = strs[0];
            for(int i=1;i<strs.length;i++){
                common = campare(common,strs[i]);
            }
            return common;
        }        
    }
    public String campare(String com, String s){
        String result = "";
        char[] cArray = com.toCharArray();
        char[] sArray = s.toCharArray();
        for(int i=0; i<(cArray.length<=sArray.length?cArray.length:sArray.length); i++){
            if(cArray[i] == sArray[i])
                result += cArray[i];
            else
                break;
        }
        return result;
    }
}