递归下降实现LL(1)文法分析C语言与Python实现

#include<stdio.h>

#include<string>
char str[10];
int index=0;
void E();			//E->TX;
void X();			//X->+TX | e
void T();			//T->FY
void Y();			//Y->*FY | e
void F();			//F->(E) | i
int main()
{
	int len;
	int m;
	printf("请输入要测试的次数：");
	scanf("%d",&m);
	while(m--)
	{
		printf("请输入算数表达式：");
		scanf("%s",str);
		len=strlen(str);
		str[len]='#';
		str[len+1]='\0';
		E();
		printf("正确语句！\n");
		strcpy(str,"");
		index=0;
	}
	return 0;
}
void E()
{
    T();
    X();
}
void X()
{
	if(str[index]=='+')
	{
	    index++;
		T();
		X();
	} 
}
void T()
{
	F();
	Y();
}
void Y()
{
	if(str[index]=='*')
	{
        index++;
		F();
		Y();
	}
}
void F()
{
	if(str[index]=='i')
	{
		index++;
	}
	else if (str[index]=='(')
	{	 
		index++;
		E();
		if(str[index]==')')
		{
			index++; 
		}else{
			printf("\n分析失败!\n");
			exit (0);
		}
	} 
	else{
		printf("分析失败!\n"); 
		exit(0);
	}
 }

'''
E->TM
M->+TM|~
T->FN
N->*FN|~
F->i|(E)
'''


import time
index = 0


def ParseE():
    ParseT()
    ParseM()


def ParseM():
    global index
    if strx[index] == '+':
        index += 1
        ParseT()
        ParseM()


def ParseT():
    ParseF()
    ParseN()


def ParseN():
    global index
    if strx[index] == '*':
        index += 1
        ParseF()
        ParseN()


def ParseF():
    global index
    if strx[index] == 'i':
        index += 1
    elif strx[index] == '(':
        index += 1
        ParseE()
        if strx[index] == ')':
            index += 1
        else:
            print('NO,输入不合法')
    else:
        print('NO,输入不合法')


strx_ = input('输入表达式')
#strx_ = 'i+i*i'
a = time.clock()
strx_ += '#'
x = 1
while x:
    index = 0
    strx = strx_
    strx += '#'
    ParseE()
    x -= 1

b = time.clock()
print(b-a)