#define MAX 100
#include <iostream>
using namespace std;
#include <string.h>
#include <stdlib.h>
//函数声明
void input();
void init_stack();
void ll1_analyzing();
void ll1array_push(char);
int is_Vt();
int is_ll1array(char);
int Vn_index();
int Vt_index(char);
void pop();
void push(char);
void reverse();
int printerror();
//全局变量定义
//LL(1)表一
//定义LL(1)分析表
char Vn_array[] = "ABCDE";
char Vt_array[] = "i+*()#";
char *LL1_array[][6] = {
{"CB", " ", " ", "CB", " ", " "},
{" ", "+CB", " ", " ", "u", "u"},
{"ED", " ", " ", "ED", " ", " "},
{" ", "u", "*ED", " ", "u", "u"},
{"i", " ", " ", "(A)", " ", " "}
};
//end
/*
//LL(1)表二
//定义LL(1)分析表
char Vn_array[] = "PDEFS";
char Vt_array[] = "bdes;#";
char *LL1_array[][6] = {
{"bDSe", " ", " ", " ", " ", "bDSe "},
{" ", "d;E", " ", " ", " ", " "},
{" ", "D", " ", "u", " ", " "},
{" ", " ", "u", " ", ";sF", "u"},
{" ", " ", " ", "sF", " ", " "}
};
//end
*/
char analyzed_sentence[MAX];
char stack[MAX];
char top;
char *temp;
char identified[MAX];
int n=0;
void main()
{
input();
init_stack(); //初始化栈，将'#'和开始符进栈
ll1_analyzing();
}
void input()
{
int ch=0;
int i=0;
while((ch=cin.get()) != '#') {
analyzed_sentence[i] = ch;
i++;
}
analyzed_sentence[i] = '#';
}
void init_stack()
{
stack[0] = '#';
stack[1] = Vn_array[0]; //开始符进栈
cout << stack[1] << "->";
}
void ll1_analyzing()
{
top = stack[1];
int error;
for (int i=0;i<=strlen(analyzed_sentence);i++) {
int test;
test = is_Vt();
if (1 == test) {
if (top == analyzed_sentence[i]) {
identified[n++] = top;
pop();
continue;
}
else {
printerror();
break;
}
}
else if ('#' == top) { //结束，将最终的表达式打印出来，除了'#'
for (int p=0;p<strlen(analyzed_sentence)-1;p++) {
printf("%c", analyzed_sentence[p]);
}
break;
}
else {
do {
int judge=0;
judge = is_ll1array(analyzed_sentence[i]);
if (judge == 1) {
if (1 == is_Vt()) { //假设有符号不匹配，出错
error=printerror();
break;
}
ll1array_push(analyzed_sentence[i]);
}
else {
error = printerror();
break;
}
}
while (top != analyzed_sentence[i]);
if (error == 1)
break;
identified[n++] = top;
if (top != '#')
pop();
}
}
}
void ll1array_push(char currentchar)
{
int i,j;
i=Vn_index(); //求栈顶元素在Vn数组里面的下标
j=Vt_index(currentchar); //求当前处理的符号在Vt数组里面的下标
temp=LL1_array[i][j];
reverse();
pop();
int k;
for(k=0;k<strlen(temp);k++)
{
push(temp[k]);
}
printf("%s", identified);
for (int m=strlen(stack)-1;m>0;m--)
cout << stack[m] ;
cout << "->";
if (top == 'u')
pop();
}
void pop()
{
int topnum;
topnum = strlen(stack)-1;
stack[topnum] = '\0';
top = stack[topnum-1];
}
void push(char element)
{
int topnum;
topnum = strlen(stack);
stack[topnum] = element;
top = element;
}
int is_Vt()
{
int i;
int hit=0;
for (i=0;i<strlen(Vt_array);i++) {
if(top == Vt_array[i])
hit = 1;
}
if (top == '#')
hit = 0;
if (hit == 1)
return 1;
else
return -1;
}
int is_ll1array(char currentchar)
{
int i,j;
i=Vn_index(); //求栈顶元素在Vn数组里面的下标
j=Vt_index(currentchar); //求当前处理的符号在Vt数组里面的下标
if (LL1_array[i][j] == " ") {
return -1;
}
else
return 1;
}
int Vn_index()
{
for(int i=0;i<strlen(Vn_array);i++) {
if (top == Vn_array[i])
return i;
}
return -1;
}
int Vt_index(char index_array)
{
for(int i=0;i<strlen(Vt_array);i++) {
if (index_array == Vt_array[i])
return i;
}
return -1;
}
void reverse() //逆序处理
{
char s[MAX];
strcpy(s, temp);
int i,j;
char tem;
i=0;
while (s[i] != '\0')
++i;
--i;
if (s[i] == '\n')
--i;
j=0;
while (j<i)
{
tem = s[j];
s[j] = s[i];
s[i] = tem;
--i;
++j;
}
temp=s;
}
int printerror()
{
cout << "这不是一句合法的句子，无法推导！" <<endl;
return 1;
}
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