LL1语法分析器c语言代码

以下是一个简单的LL(1)语法分析器的C++代码，用于解析给定文法的输入字符串：

#include <iostream>
#include <stack>
#include <map>
#include <vector>
#include <string>

using namespace std;

// 定义文法规则
vector<string> grammar = {
    "E->TE'",
    "E'->+TE'|ε",
    "T->FT'",
    "T'->*FT'|ε",
    "F->a|(E)"
};

// 定义预测分析表
map<pair<string, string>, string> parse_table = {
    {{"E", "a"}, "TE'"},
    {{"E", "("}, "TE'"},
    {{"E'", "+"}, "+TE'"},
    {{"E'", ")"}, "ε"},
    {{"E'", "$"}, "ε"},
    {{"T", "a"}, "FT'"},
    {{"T", "("}, "FT'"},
    {{"T'", "+"}, "ε"},
    {{"T'", "*"}, "*FT'"},
    {{"T'", ")"}, "ε"},
    {{"T'", "$"}, "ε"},
    {{"F", "a"}, "a"},
    {{"F", "("}, "(E)"}
};

// 定义符号栈和输入串栈
stack<string> symbol_stack;
stack<char> input_stack;

// 初始化输入串栈
void init_input_stack(string input) {
    for (int i = input.length() - 1; i >= 0; i--) {
        input_stack.push(input[i]);
    }
    input_stack.push('$');
}

// 获取产生式右部
string get_production(string left_symbol, string input_symbol) {
    if (parse_table.find({left_symbol, input_symbol}) != parse_table.end()) {
        return parse_table[{left_symbol, input_symbol}];
    }
    return "";
}

// LL(1)语法分析
bool parse(string input) {
    // 初始化符号栈和输入串栈
    symbol_stack.push("$");
    symbol_stack.push("E");
    init_input_stack(input);

    // 语法分析
    while (!symbol_stack.empty()) {
        string top_symbol = symbol_stack.top();        char top_input = input_stack.top();

        if (top_symbol == "$" && top_input == '$') {
            return true;
        }

        if (top_symbol == top_input || top_symbol == "ε") {
            symbol_stack.pop();
            input_stack.pop();
        } else if (top_symbol == "a" && top_input == 'a') {
            symbol_stack.pop();
            input_stack.pop();
        } else if (top_symbol == "(" && top_input == ')') {
            symbol_stack.pop();
            input_stack.pop();
        } else if (top_symbol == "E" || top_symbol == "T" || top_symbol == "F") {
            string production = get_production(top_symbol, string(1, top_input));
            if (production == "") {
                return false;
            }
            symbol_stack.pop();
            if (production != "ε") {
                for (int i = production.length() - 1; i >= 0; i--) {
                    symbol_stack.push(string(1, production[i]));
                }
            }
        } else {
            return false;
        }
    }

    return true;
}

int main() {
    string input = "a*(a+a)$";
    if (parse(input)) {
        cout << "输入串 " << input << " 符合文法规则" << endl;
    } else {
        cout << "输入串 " << input << " 不符合文法规则" << endl;
    }

    return 0;
}