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。