给你一个字符串 s 和一个字符规律 p，请你来实现一个支持 '.' 和 '*' 的正则表达式匹配。
'.'匹配任意单个字符'*'匹配零个或多个前面的那一个元素
所谓匹配，是要涵盖 整个 字符串 s的，而不是部分字符串。
示例 1：
输入：s = "aa", p = "a"
输出：false
解释："a" 无法匹配 "aa" 整个字符串。示例 2:
输入：s = "aa", p = "a*"
输出：true
解释：因为 '*' 代表可以匹配零个或多个前面的那一个元素, 在这里前面的元素就是 'a'。因此，字符串 "aa" 可被视为 'a' 重复了一次。示例 3：
输入：s = "ab", p = ".*"
输出：true
解释：".*" 表示可匹配零个或多个（'*'）任意字符（'.'）。class Solution {
public boolean isMatch(String s, String p) {
Match first = getMatch(p);
Match match =first;
while (match != null){
match.s = s;
match = match.next;
}
return first.match();
}
public Match getMatch(String p){
Match first = null;
Match match = null;
StringBuilder sb = new StringBuilder();
for (int i = 0; i < p.length(); i++) {
char c = p.charAt(i);
if(c <='z' && c >='a'){
sb.append(c);
continue;
}
if(c == '.'){
if(sb.length() >0){
StringMatch stringMatch = new StringMatch();
stringMatch.p = sb.toString();
if(match == null){
match = stringMatch;
first = match;
}else{
match.next = stringMatch;
match = match.next;
}
sb.delete(0,sb.length());
}
int nums = 1;
boolean ended =true;
while (++i < p.length()){
if(p.charAt(i) == '.'){
nums++;
continue;
}else if(p.charAt(i) == '*'){
if(nums >1){
PointMatch pointMatch = new PointMatch();
pointMatch.nums = nums-1;
if(match == null){
match = pointMatch;
first = match;
}else{
match.next = pointMatch;
match = match.next;
}
}
PointXing pointXing = new PointXing();
if(match == null){
match = pointXing;
first = match;
}else{
match.next = pointXing;
match = match.next;
}
}else{
PointMatch pointMatch = new PointMatch();
pointMatch.nums = nums;
if(match == null){
match = pointMatch;
first = match;
}else{
match.next = pointMatch;
match = match.next;
}
i--;
}
ended = false;
break;
}
if(ended){
PointMatch pointMatch = new PointMatch();
pointMatch.nums = nums;
if(match == null){
match = pointMatch;
first = match;
}else{
match.next = pointMatch;
match = match.next;
}
break;
}
}else{
//c == '*'
if(sb.length() == 0){
continue;
}
char c1 = sb.charAt(sb.length() - 1);
sb.deleteCharAt(sb.length() - 1);
if(sb.length() >0){
StringMatch stringMatch = new StringMatch();
stringMatch.p = sb.toString();
if(match == null){
match = stringMatch;
first = match;
}else{
match.next = stringMatch;
match = match.next;
}
sb.delete(0,sb.length());
}
CharXingMatch charXingMatch = new CharXingMatch();
charXingMatch.c = c1;
if(match == null){
match = charXingMatch;
first = match;
}else{
match.next = charXingMatch;
match = match.next;
}
}
}
if(sb.length() >0){
StringMatch stringMatch = new StringMatch();
stringMatch.p = sb.toString();
if(match == null){
match = stringMatch;
first = match;
}else{
match.next = stringMatch;
match = match.next;
}
}
return first;
}
class Match{
int start;
int end;
String s;
boolean isMatch;
Match next;
//匹配
public boolean match(){
if(null == next){
return matchEnd();
}
return matchNormal();
}
protected boolean matchNormal() {
for (int i = start; i <= end ; i++) {
tryMatch(i);
if(isMatch){
if(next.match()){
return true;
}
}
}
return false;
}
protected boolean matchEnd(){
return true;
}
protected boolean tryMatch(int index){
return true;
}
//返回是否match
public boolean isMatch(){
return isMatch;
}
}
class StringMatch extends Match{
String p;
@Override
public String toString() {
return p+"start = "+start+" end="+end;
}
@Override
protected boolean matchEnd() {
isMatch = false;
if(p.length() < s.length()-end || p.length() >s.length()-start){
return false;
}
for (int i = 1; i <= p.length(); i++) {
if(p.charAt(p.length()-i) != s.charAt(s.length()-i)){
return false;
}
}
isMatch = true;
return true;
}
@Override
protected boolean tryMatch(int index) {
isMatch = false;
if(p.length() > s.length()-index){
return false;
}
for (int i = 0; i < p.length(); i++) {
if(p.charAt(i) != s.charAt(i+index)){
return false;
}
}
next.start = p.length()+index;
next.end = p.length()+index;
isMatch = true;
return true;
}
}
class PointMatch extends Match{
int nums;
@Override
public String toString() {
return "pointMatch,nums = "+nums+" start = "+start+" end="+end;
}
@Override
protected boolean matchEnd() {
isMatch = false;
if(nums+end >=s.length() && nums+start <= s.length()){
isMatch = true;
}
return isMatch;
}
@Override
protected boolean tryMatch(int index) {
isMatch = false;
if(nums > s.length()-index){
return false;
}
next.start = nums+index;
next.end = nums+index;
isMatch = true;
return true;
}
}
class CharXingMatch extends Match{
char c;
int skip;
@Override
public String toString() {
return "CharXingMatch,c="+c+" start = "+start+" end="+end;
}
protected boolean matchNormal() {
for (int i = start; i <= end ; i=i+skip) {
tryMatch(i);
if(isMatch){
if(next.match()){
return true;
}
}
}
return false;
}
@Override
protected boolean matchEnd() {
isMatch = false;
for (int i = end; i < s.length(); i++) {
if(c != s.charAt(i)){
return false;
}
}
isMatch = true;
return true;
}
@Override
protected boolean tryMatch(int index) {
next.start = index;
while (index <s.length() && c == s.charAt(index)){
index++;
}
next.end = index;
skip = next.end - next.start+1;
isMatch = true;
return true;
}
}
class PointXing extends Match{
@Override
public String toString() {
return "PointXing"+" start = "+start+" end="+end;
}
protected boolean matchNormal() {
next.start = start;
next.end = Math.max(s.length(),start);
return next.match();
}
@Override
protected boolean matchEnd() {
isMatch = true;
return true;
}
}
}