-
Notifications
You must be signed in to change notification settings - Fork 0
/
util.h
95 lines (85 loc) · 3.05 KB
/
util.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
#ifndef __UTIL_H__
#define __UTIL_H__
#include <iostream>
#include <stack>
#include <string>
#include <vector>
class Rgex {
public:
struct RgexToken {
char c; // 符号
bool op; // 是不是正则的运算符
RgexToken(char c, bool op) : c(c), op(op) {}
};
static int priority(char c) {
if (c == '|')
return 1;
else if (c == '.')
return 2;
else if (c == '*')
return 3;
else
return -1;
}
// 转逆波兰表达式
static std::vector<RgexToken> toRPN(const std::string& infix) {
std::stack<char> st;
std::vector<RgexToken> tokens;
// 1.先全部转成token
for (int i = 0; i < infix.length(); ++i) {
char c = infix[i];
// 处理转义字符
if (c == '\\')
tokens.push_back(RgexToken(infix[++i], false));
else if (c == '*' || c == '|' || c == '(' || c == ')')
tokens.push_back(RgexToken(c, true));
else
tokens.push_back(RgexToken(c, false));
}
// 2.处理缺少'.'运算符
for (int i = 0; i < tokens.size(); ++i) {
RgexToken token = tokens[i];
if (token.op) {
if (i + 1 < tokens.size() && token.c != '(' && tokens[i + 1].c != ')' && token.c != '|' && tokens[i + 1].c != '|' && tokens[i + 1].c != '*')
tokens.insert(tokens.begin() + ++i, RgexToken('.', true));
else if (i + 1 < tokens.size() && !tokens[i + 1].op && token.c != '(' && token.c != '|')
tokens.insert(tokens.begin() + ++i, RgexToken('.', true));
} else {
if (i + 1 < tokens.size())
if (tokens[i + 1].op && tokens[i + 1].c == '(')
tokens.insert(tokens.begin() + ++i, RgexToken('.', true));
else if (!tokens[i + 1].op)
tokens.insert(tokens.begin() + ++i, RgexToken('.', true));
}
}
// 3. 转后缀表达式
std::vector<RgexToken> res;
std::stack<RgexToken> operStack;
for (int i = 0; i < tokens.size(); ++i) {
RgexToken token = tokens[i];
if (!token.op) {
res.push_back(token);
} else if (token.c == '(') {
operStack.push(token);
} else if (token.c == ')') {
while (operStack.top().c != '(') {
res.push_back(operStack.top());
operStack.pop();
}
operStack.pop();
} else {
while (operStack.size() != 0 && priority(token.c) <= priority(operStack.top().c)) {
res.push_back(operStack.top());
operStack.pop();
}
operStack.push(token);
}
}
while (!operStack.empty()) {
res.push_back(operStack.top());
operStack.pop();
}
return res;
}
};
#endif // __UTIL_H__