Algorithms—14.Longest Common Prefix

思路：先比较前2个String，找出公共开头，然后从第三个开始逐次比较，当公共开头字符串长度为0时，直接返回""；

public class Solution {
public String longestCommonPrefix(String[] strs) {
if (strs.length==0) {
return "";
}
if (strs.length==1) {
return strs[0];
}
int n=0;
if (strs[0].length()<strs[1].length()) {
n=strs[0].length();
}else {
n=strs[1].length();
}
String answer="";
for (int i = 0; i < n; i++) {
String k0=strs[0].substring(i,i+1);
String k1=strs[1].substring(i,i+1);
if (k0.equals(k1)) {
answer+=k0;
}else {
break;
}
}
if (strs.length==2) {
return answer;
}
for (int i = 2; i < strs.length; i++) {
if (answer.length()==0) {
return "";
}
int length=0;
String k="";
if (strs[i].length()<answer.length()) {
length=strs[i].length();
}else {
length=answer.length();
}
while (!answer.substring(0, length).equals(strs[i].substring(0, length))) {
length--;
}
answer=answer.substring(0,length);
}
return answer;

}
}

耗时：320ms，处于中游，一次编译通过，哇哈哈。