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Parser.java
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106 lines (96 loc) · 3.38 KB
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package regex;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
/**
* @author cyb
*/
public class Parser {
/**
* 操作符优先级
*/
public static HashMap<Character, Integer> operatorPrecedence = new HashMap<>() {{
put('|', 0);
put('&', 1);
put('*', 2);
put('+', 2);
put('?', 2);
put('{', 2);
}};
public static ArrayList<Atom> insertExplicitConcatOperator(String s) {
ArrayList<Atom> list = new ArrayList<>();
for (int i = 0; i < s.length(); i++) {
char token = s.charAt(i);
if (token == '\\') {
// 字符集
if (i == s.length() - 1) {
throw new RuntimeException("非法转义字符");
}
char next = s.charAt(i + 1);
if (String.valueOf(next).matches("[^dDwWsS]")) {
throw new RuntimeException("非法转义字符");
}
list.add(new Atom("\\" + next));
i += 1;
} else if (token == '{') {
// { } 量词
StringBuilder stringBuilder = new StringBuilder("{");
int count = 1;
while (i + count < s.length()) {
char next = s.charAt(i + count);
stringBuilder.append(next);
count++;
if (next == '}') {
break;
}
}
list.add(new Atom(stringBuilder.toString()));
i += count - 1;
} else {
list.add(new Atom(token));
}
if (token == '(' || token == '|') {
continue;
}
if (i < s.length() - 1) {
// 是否需要显示连接运算符
char next = s.charAt(i + 1);
if (next == '*' || next == '|' || next == ')' || next == '+' || next == '?' || next == '{') {
continue;
}
list.add(new Atom('&'));
}
}
return list;
}
@SuppressWarnings("all")
public static ArrayList<Atom> toPostfix(ArrayList<Atom> list) {
ArrayList<Atom> res = new ArrayList<>();
Deque<Atom> operatorStack = new ArrayDeque<>();
for (int i = 0; i < list.size(); i++) {
Atom token = list.get(i);
if (token.getS().matches("[&|*+?]|(\\{.+)")) {
while (!operatorStack.isEmpty() && !operatorStack.peek().getS().equals("(")
&& operatorPrecedence.get(operatorStack.peek().getS().charAt(0)) >= operatorPrecedence.get(token.getS().charAt(0))) {
res.add(operatorStack.pop());
}
operatorStack.push(token);
} else if (token.getS().equals("(")) {
operatorStack.push(token);
} else if (token.getS().equals(")")) {
while (!operatorStack.peek().getS().equals("(")) {
res.add(operatorStack.pop());
}
// pop 左括号
operatorStack.pop();
} else {
res.add(token);
}
}
while (!operatorStack.isEmpty()) {
res.add(operatorStack.pop());
}
return res;
}
}