编译原理——预测表C语言实现

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
/* 广西师范大学 计算机科学与工程学院 GuangXi Normal University College of Computer Science and Engineering Student STZ */ 

string map[6][7]={
    
	{
     "",  "i",  "+",  "*",  "(",")","#"}, 
	{
    "E", "TD",   "",   "", "TD", "", ""},
	{
    "D",   "","+TD",   "",   "","e","e"},
	{
    "T", "FS",   "",   "", "FS", "", ""},
	{
    "S",   "",  "e","*FS",   "","e","e"},
	{
    "F",  "i",   "",   "","(E)", "", ""},
};

char input[] = "i+i*i#";
char start[] = "#E";


void match(int l,int c){
    
// int len = map[l][c].length();//替换串的长度 
	int i = 0;
	int isfirst = 0;
	cout<<start[strlen(start)-1]<<"->"<<map[l][c]<<endl;
	for(string::reverse_iterator iter=map[l][c].rbegin();iter!=map[l][c].rend();iter++){
    //反向迭代 
		if(isfirst==0){
    
			start[strlen(start)-1] = *iter;
			isfirst=1;
		}else{
    
			start[strlen(start)] = *iter;
		}
		for(int j=0;j<6;j++){
    
			printf("%c",start[j]);
		}cout<<endl;
}

int analysis(char l,char c){
    
	int flag = 1; 
	int i,j;
	string L = "";
	L += l;
	string C = "";
	C +=c;
	//cout<<l<<endl;
	for(i=1;i<6;++i){
     
		if(L.compare(map[i][0])==0){
    //匹配到行 
			break; 
		} 
	}	
// cout<<i<<endl; 
// i--;
	for(j=1;j<7;++j){
    
		if(C.compare(map[0][j])==0){
    //匹配到列
			break; 
		}
	}	
// cout<<j<<endl; 
// j--;
	if(map[0][j].compare("")!=0){
    
		match(i,j);// 
		return 1;
		}else{
    
			cout<<l<<"不匹配"<<map[0][j]<<" map为："<<map[i][j]<<endl; 
			return 0;
		}
}

int main(){
    
	 		int flag = 1;	
			while(flag){
    
				cout<<endl<<"当前start状态：";
					for(int j=0;j<6;j++){
    
						printf("%c",start[j]);
					}cout<<endl;
				cout<<"当前input状态："<<input<<endl; 
				if(start[strlen(start)-1] == input[0]){
    //如果栈尾和剩余字符串队首一样先消除；
					start[strlen(start)-1]='\0';
					for(int i=0;i<strlen(input)-1;i++){
    
						input[i] = input[i+1];
					}
					input[strlen(input)-1]='\0';
					cout<<endl<<"消除成功！\n当前start状态："<<start<<"\n当前input状态："<<input<<endl; 
				}
				else if(start[strlen(start)-1]=='e'){
    //如果最后一位是空，自动去掉 
					start[strlen(start)-1]='\0';
				}
				else
					flag = analysis(start[strlen(start)-1],input[0]);//如果栈尾和剩余字符串队首不一样；
				if(flag==0){
    
					cout<<"编译出错！！"<<endl; 
					break;
				}
				if(strlen(input)==0){
    
					cout<<"END！！"<<endl; 
					break;
				}
			} 
	return 0;
}