水题。一个一个字符串比较就是了。

public class Solution {    public String longestCommonPrefix(String[] strs) {        // Start typing your Java solution below        // DO NOT write main() function        if (strs == null || strs.length == 0) return "";    	String s = strs[0];    	for (int i = 1; i < strs.length; i++) {    		int min = Math.min(s.length(), strs[i].length());    		int j = 0;    		while (j < min && s.charAt(j) == strs[i].charAt(j)) { j++; }    		s = s.substring(0, j);    	}        return s;    }}