Adding CYK Algorithm usage in C++

4. CYK Algorithm C/cyk.cpp

@@ -0,0 +1,182 @@
+#include<iostream>  
+#include<cstring>
+#include<algorithm>
+#include<string>
+#include<cassert>
+#include<iomanip>
+using namespace std;
+
+#define MAX 100
+#define for(i,a,b) for(i=a;i<b; i++)
+
+string gram[MAX][MAX];  //to store entered grammar
+string dpr[MAX];
+int p,np;       //np-> number of productions
+
+inline string concat( string a, string b)   //concatenates unique non-terminals
+{
+    int i;
+    string r=a;
+    for(i,0,b.length())
+        if(r.find(b[i]) > r.length())
+            r+=b[i];
+    return (r);
+}
+
+inline void break_gram(string a)    //seperates right hand side of entered grammar
+{
+    int i;
+    p=0;
+    while(a.length())
+    {
+        i=a.find("|");
+        if(i>a.length())
+        {
+            dpr[p++] = a;
+            a="";
+        }
+        else
+        {
+            dpr[p++] = a.substr(0,i);
+            a=a.substr(i+1,a.length());
+        }
+    }
+}
+
+inline int lchomsky(string a)   //checks if LHS of entered grammar is in CNF
+{
+    if(a.length()==1 && a[0]>='A' && a[0]<='Z')
+        return 1;
+    return 0;
+}
+
+inline int rchomsky(string a)   //checks if RHS of grammar is in CNF
+{
+    if (a.length() == 1 && a[0]>='a' && a[0] <='z')
+        return 1;
+    if (a.length()==2 && a[0]>='A' && a[0]<='Z' && a[1]>='A' && a[1]<='Z' )
+        return 1;
+    return 0;
+}
+
+inline string search_prod(string p) //returns a concatenated string of variables which can produce string p
+{
+    int j,k;
+    string r="";
+    for(j,0,np)
+    {
+        k=1;
+        while(gram[j][k] != "")
+        {
+            if(gram[j][k] == p)
+            {
+                r=concat(r,gram[j][0]);
+            }
+            k++;
+        }
+    }   
+    return r;
+}
+
+inline string gen_comb(string a, string b)  //creates every combination of variables from a and b . For eg: BA * AB = {BA, BB, AA, BB}
+{
+    int i,j;
+    string pri=a,re="";
+    for(i,0,a.length())
+        for(j,0,b.length())
+        {
+            pri="";
+            pri=pri+a[i]+b[j];
+            re=re+search_prod(pri);     //searches if the generated productions can be created or not
+        }       
+    return re;
+}
+
+int main()
+{
+    int i,pt,j,l,k;
+    string a,str,r,pr,start;
+    cout<<"\nEnter the start Variable ";
+    cin >> start;
+    cout<<"\nNumber of productions ";
+    cin >> np;
+    for(i,0,np)
+    {
+        cin >> a;
+        pt=a.find("->");
+        gram[i][0] = a.substr(0,pt);
+        if (lchomsky(gram[i][0]) == 0)
+        {
+            cout<<"\nGrammar not in Chomsky Form";
+            abort();
+        }
+        a = a.substr(pt+2, a.length());
+        break_gram(a);
+        for(j,0,p)
+        {
+            gram[i][j+1]=dpr[j];
+            if (rchomsky(dpr[j]) == 0)
+            {
+                cout<<"\nGrammar not in Chomsky Form";
+                abort();
+            }
+        }
+    }
+    string matrix[MAX][MAX],st;
+    cout<<"\nEnter string to be checked : ";
+    cin >> str;
+    for(i,0,str.length())       //Assigns values to principal diagonal of matrix
+    {
+        r="";
+        st = "";
+        st+=str[i];
+        for(j,0,np)
+        {
+            k=1;
+            while(gram[j][k] != "")
+            {
+                if(gram[j][k] == st)
+                {
+                    r=concat(r,gram[j][0]);
+                }
+                k++;
+            }
+        }
+        matrix[i][i]=r;
+    }
+    int ii,kk;
+    for(k,1,str.length())       //Assigns values to upper half of the matrix
+    {
+        for(j,k,str.length())
+        {
+            r="";
+            for(l,j-k,j)
+            {
+                pr = gen_comb(matrix[j-k][l],matrix[l+1][j]);
+                r = concat(r,pr);
+            }
+            matrix[j-k][j] = r;
+        }
+    }
+
+    for(i,0,str.length())   //Prints the matrix
+    {
+        k=0;
+        l=str.length()-i-1;
+        for(j,l,str.length())
+        {
+            cout<<setw(5)<<matrix[k++][j]<<" ";
+        }
+        cout<<endl;
+    }
+
+    int f=0;
+    for(i,0,start.length())
+        if(matrix[0][str.length()-1].find(start[i]) <= matrix[0][str.length()-1].length())   //Checks if last element of first row contains a Start variable
+        {
+            cout<<"String can be generated\n";
+            return 0;
+        }
+    cout<<"String cannot be generated\n";
+    return 0;
+}