پروژه سی پلاس پلاس(28078)+
سه سال پیش منتشر شده
تعداد بازدید: 359
کد پروژه: 284694
شرح پروژه
:
سلام وقت بخير كدي به زبان سي پلاس پلاس دارم اما داراي مشكل هستش ميتونيد اصلاحش كنيد؟
#include<iostream>
#include<fstream>
#include<string>
#include<vector>
using namespace std;
/*
function to read grammar from a file
the function pushes each production in vector pro
*/
void ReadGrammar(string file, vector<string>& pro)
{
string line;
ifstream myfile;
myfile.open(file);
while (getline(myfile, line))
{
pro.push_back(line);
}
}
/*
function to check if we can derive string str[]
using productions in pro
*/
bool RecognizeString(vector<string>& pro, string str)
{
int n, v, s, p, i, l;
n = str.length();
v = pro.size();
/*
3D vector dp[n+1, n+1, 26]
*/
vector< vector< vector<bool> > > dp(n + 1, vector< vector <bool> >(n + 1, vector<bool>(26, false)));
/*
the following loop recognize substrings of length 1
*/
for (s = 0; s < n; ++s)
{
/* reading each production */
for (i = 0; i < v; ++i)
{
/*
if pro[i].length == 4 then it means that the production pro[i]
is in form P->a
pro[i][3] == str[s] checks if production P->a can recognize the character str[s]
*/
if (pro[i].length() == 4 && pro[i][3] == str[s])
{
dp[1][s][pro[i][0] - 'A'] = true;
}
}
}
/*
the following loop recognize substrings of length > 1
l is the length of the current substring
*/
for (l = 2; l <= n; ++l)
{
/* s is the starting index of substring */
for (s = 0; s < n - l + 1; ++s)
{
/* p is the size of left partition of the substring */
for (p = 1; p <= l - 1; ++p)
{
/* reading each production */
for (i = 0; i < v; ++i)
{
/*
if pro[i].length() == 5 then it implies that the production is in form P->AB
dp[ p ][ s ][ pro[i][3]-'A'] checks if we can derive left partition using A
dp[ l-p ][ s+p ][ pro[i][4]-'A' ] checks if we can derive the right partition using B
*/
if (pro[i].length() == 5 && dp[p][s][pro[i][3] - 'A'] && dp[l - p][s + p][pro[i][4] - 'A'])
{
dp[l][s][pro[i][0] - 'A'] = true;
}
}
}
}
}
return dp[n][0]['S' - 'A'];
}
int main()
{
vector<string> pro;
string str;
ofstream myfile("text.txt");
ReadGrammar("text.txt", pro);
cout << "Context-free Grammar" << endl;
for (int i = 0; i < pro.size(); ++i)
{
cout << pro[i] << endl;
}
cout << "Enter a String: ";
cin >> str;
if (RecognizeString(pro, str))
cout << "The input string can be derived using given CFL" << endl;
else
cout << "The input string cannot be derived using given CFL" << endl;
}
Context-free Grammar
S->AB
A->a
A->BB
B->AS
B->b
Enter a String: aabbb
The input string can be derived using given CFL
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+++
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