C# LL(1) 文法预测分析表构造算法实现

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows.Forms;
using static System.Windows.Forms.VisualStyles.VisualStyleElement;

namespace byyljxfzxt
{
    public partial class Form4 : Form
    {
        public Form4()
        {
            InitializeComponent();
        }

        //--------------------预处理
        Dictionary<string, List<string>> production;
        Dictionary<string, List<string>> firsts;
        Dictionary<string, List<string>> follows;
        List<string> terminals;
        List<string> nonterminals;

        private void button4_Click(object sender, EventArgs e)
        {
            string text = richTextBox1.Text;
            production = new Dictionary<string, List<string>>();
            string[] pro = text.Split('
');
            foreach (string s in pro)
            {
                if (s == "") continue;

                Regex.Replace(s, " ", "");
                string[] ga = Regex.Split(s, "->");
                if (ga.Length != 2) return;
                if (ga[0].Length == 0 || ga[1].Length == 0)
                    return;
                if (ga[0].Length != 1 || !char.IsUpper(ga[0][0])) return;

                string[] ga2 = Regex.Split(ga[1], "\|");
                if (!production.ContainsKey(ga[0]))
                    production.Add(ga[0], new List<string>());
                foreach (string s1 in ga2)
                    production[ga[0]].Add(s1);
            }

            firsts = new Dictionary<string, List<string>>();
            foreach (var item in production.Keys)
                GetFirst(item, production, firsts);

            follows = new Dictionary<string, List<string>>();
            foreach (var item in production.Keys)
                GetFollow(item, production, firsts, follows);


            if (JudgeLL1(production, firsts, follows))
            {
                MessageBox.Show("该文法是LL(1)文法\n");
                
            }
            else
            {
                MessageBox.Show("该文法不是LL(1)文法，存在左递归或者存在FIRST集合有交集的情况！\n");
            }
            button1.Enabled = true;
            button2.Enabled = true;
            button3.Enabled = true;

        }

        private void button6_Click(object sender, EventArgs e)
        {
            //构造预测分析表
            Dictionary<string, Dictionary<string, string>> table = new Dictionary<string, Dictionary<string, string>>();
            foreach (var nonterminal in nonterminals)
            {
                table.Add(nonterminal, new Dictionary<string, string>());
                foreach (var terminal in terminals)
                {
                    table[nonterminal].Add(terminal, "");
                }
            }

            foreach (var item in production)
            {
                string A = item.Key;
                foreach (var prod in item.Value)
                {
                    var select = new Select(new LL1Item(item.Key, prod), firsts, follows);
                    foreach (var t in select.getselects()[A][prod])
                    {
                        if (table[A][t] != "")
                        {
                            MessageBox.Show("该文法不是LL(1)文法，存在冲突！\n");
                            return;
                        }
                        table[A][t] = prod;
                    }
                }
            }

            //输出预测分析表
            listView3.Clear();
            foreach (var terminal in terminals)
            {
                listView3.Columns.Add(terminal, 100, HorizontalAlignment.Center);
            }
            foreach (var nonterminal in nonterminals)
            {
                ListViewItem lvi = new ListViewItem(nonterminal);
                foreach (var terminal in terminals)
                {
                    lvi.SubItems.Add(table[nonterminal][terminal]);
                }
                listView3.Items.Add(lvi);
            }
        }

        
        private void GetFirst(string symbol, Dictionary<string, List<string>> production1, Dictionary<string, List<string>> firsts1)
        {
            // 如果该非终结符的 FIRST 集已经被计算出，则直接返回
            if (firsts1.ContainsKey(symbol))
            {
                return;
            }
            firsts1.Add(symbol, new List<string>());
            // 遍历产生式，计算 FIRST 集
            foreach (var prod in production1[symbol])
            {
                // 如果产生式首字符为终结符，则直接将其加入 FIRST 集中
                if (prod.Length > 0 && IsTerminal(prod[0]))
                {
                    if (!firsts1[symbol].Contains(prod[0].ToString()))
                        firsts1[symbol].Add(prod[0].ToString());
                    continue;
                }
                // 如果产生式首字符为非终结符，则计算该非终结符的 FIRST 集，并将结果加入首字符的 FIRST 集中
                else if (prod.Length > 0 && !IsTerminal(prod[0]))
                {
                    GetFirst(prod[0].ToString(), production1, firsts1);
                    foreach (var f in firsts1[prod[0].ToString()])
                    {
                        if (!firsts1[symbol].Contains(f) && !f.Equals('#'))
                            firsts1[symbol].Add(f);
                    }
                }
                //如果第一个非终结符能推出#
                if (IsReachEmpty(prod[0].ToString(), production1))
                {
                    // 递归计算第二个和后面的字符的 FIRST 集，并将结果加入该非终结符的 FIRST 集中
                    for (int j = 1; j < prod.Length; j++)
                    {
                        if (IsTerminal(prod[j]))
                        {
                            if (!firsts1[symbol].Contains(prod[j].ToString()))
                                firsts1[symbol].Add(prod[j].ToString());
                            break;
                        }
                        GetFirst(prod[j].ToString(), production1, firsts1);
                        foreach (var f in firsts1[prod[j].ToString()])
                        {
                            if (!firsts1[symbol].Contains(f) && !f.Equals('#'))
                                firsts1[symbol].Add(f);
                        }
                        // 如果该非终结符的 FIRST 集没有包含空串，则可以结束循环
                        if (!IsReachEmpty(prod[j].ToString(), production1))
                        {
                            break;
                        }
                        // 如果是最后一个字符且所有非终结符的 FIRST 集都含有空串，则将空串加入该非终结符的 FIRST 集中
                        if (j == prod.Length - 1)
                        {
                            if (!firsts1[symbol].Contains("#"))
                                firsts1[symbol].Add("#");
                        }
                    }
                }
            }
        }

       
        // 计算 FOLLOW 集
        private void GetFollow(string symbol, Dictionary<string, List<string>> production1, Dictionary<string, List<string>> firsts1, Dictionary<string, List<string>> follows1)
        {
            // 如果该非终结符的 FOLLOW 集已经被计算出，则直接返回
            if (follows1.ContainsKey(symbol))
            {
                return;
            }
            follows1.Add(symbol, new List<string>());
            // 如果是起始符号，则将 # 加入 FOLLOW 集中
            if (symbol.Equals(production1.Keys.First()))
            {
                if (!follows1[symbol].Contains("#"))
                    follows1[symbol].Add("#");
            }
            // 遍历产生式，计算 FOLLOW 集
            foreach (var item in production1)
            {
                foreach (var prod in item.Value)
                {
                    int index = prod.IndexOf(symbol);
                    if (index == -1)
                        continue;
                    // 如果该非终结符位于产生式末尾，则将产生式左部的 FOLLOW 集加入该非终结符的 FOLLOW 集中
                    if (index == prod.Length - 1)
                    {
                        GetFollow(item.Key, production1, firsts1, follows1);
                        foreach (var f in follows1[item.Key])
                        {
                            if (!follows1[symbol].Contains(f))
                                follows1[symbol].Add(f);
                        }
                    }
                    else
                    {
                        // 如果该非终结符后面是终结符，则将该终结符加入该非终结符的 FOLLOW 集中
                        if (IsTerminal(prod[index + 1]))
                        {
                            if (!follows1[symbol].Contains(prod[index + 1].ToString()))
                                follows1[symbol].Add(prod[index + 1].ToString());
                        }
                        // 如果该非终结符后面是非终结符，则将该非终结符的 FIRST 集加入该非终结符的 FOLLOW 集中
                        else
                        {
                            GetFirst(prod[index + 1].ToString(), production1, firsts1);
                            foreach (var f in firsts1[prod[index + 1].ToString()])
                            {
                                if (!f.Equals("#") && !follows1[symbol].Contains(f))
                                    follows1[symbol].Add(f);
                            }
                            // 如果该非终结符后面的所有符号都能推出空串，则将产生式左部的 FOLLOW 集加入该非终结符的 FOLLOW 集中
                            if (IsReachEmpty(prod[index + 1].ToString(), production1))
                            {
                                GetFollow(item.Key, production1, firsts1, follows1);
                                foreach (var f in follows1[item.Key])
                                {
                                    if (!follows1[symbol].Contains(f))
                                        follows1[symbol].Add(f);
                                }
                            }
                        }
                    }
                }
            }
        }

      
    }
}

// Select 类
public class Select
{
    LL1Item LL1Item;
    First first;
    Follow follow;
    Dictionary<string, Dictionary<string, List<string>>> selects;

    public Select(LL1Item LL1Item, First first, Follow follow)
    {
        this.LL1Item = LL1Item;
        this.first = first;
        this.follow = follow;
        selects = new Dictionary<string, Dictionary<string, List<string>>>();
        GetSelect();
    }

    public void GetSelect()
    {
        var production = LL1Item.getproduction();
        foreach (var nofinal in LL1Item.nofinal)
        {
            selects.Add(nofinal, new Dictionary<string, List<string>>());
            //对非终结符的每个产生式获取select值
            foreach (var f in production[nofinal])
            {
                selects[nofinal].Add(f, new List<string>());
                for (int i = 0; i < f.Length; i++)
                {
                    //如果该产生式第一个字符为终结符
                    if (IsTerminal(f[i]))
                    {
                        if (f[i].Equals('#'))
                        {
                            foreach (var fol in follow.getfollows()[nofinal])
                                selects[nofinal][f].Add(fol);
                        }
                        else if (!selects[nofinal][f].Contains(f[i].ToString()))
                            selects[nofinal][f].Add(f[i].ToString());
                        break;
                    }
                    //如果该产生式第一个字符为非终结符
                    else
                    {
                        int flag = 0;
                        foreach (var fir in first.getfirsts()[f[i].ToString()])
                        {
                            if (fir.Equals("#"))
                                flag = 1;
                            else
                            {
                                if (!selects[nofinal][f].Contains(fir))
                                    selects[nofinal][f].Add(fir);
                            }
                        }
                        if (flag == 0) break;
                    }
                    if (i == f.Length - 1)
                    {
                        foreach (var fol in follow.getfollows()[nofinal])
                            if (!selects[nofinal][f].Contains(fol))
                                selects[nofinal][f].Add(fol);
                    }
                }
            }
        }
    }
    static bool IsTerminal(char symbol)
    {
        return !char.IsUpper(symbol);
    }

    public Dictionary<string, Dictionary<string, List<string>>> getselects()
    {
        return selects;
    }
}

// LL1Item 类
public class LL1Item
{
    public string nonterminal;
    public string prod;
    public List<string> nofinal;
    public Dictionary<string, List<string>> production;

    public LL1Item(string nonterminal, string prod, Dictionary<string, List<string>> production)
    {
        this.nonterminal = nonterminal;
        this.prod = prod;
        this.production = production;
        this.nofinal = new List<string>();
        for (int i = 0; i < prod.Length; i++)
        {
            if (!IsTerminal(prod[i]))
            {
                nofinal.Add(prod[i].ToString());
            }
        }
    }

    public Dictionary<string, List<string>> getproduction()
    {
        return production;
    }
}

// First 类
public class First
{
    Dictionary<string, List<string>> firsts;

    public First(Dictionary<string, List<string>> firsts)
    {
        this.firsts = firsts;
    }

    public Dictionary<string, List<string>> getfirsts()
    {
        return firsts;
    }
}

// Follow 类
public class Follow
{
    Dictionary<string, List<string>> follows;

    public Follow(Dictionary<string, List<string>> follows)
    {
        this.follows = follows;
    }

    public Dictionary<string, List<string>> getfollows()
    {
        return follows;
    }
}