Mi manual de algoritmos/version_actual/src/misc/parser_recursivo_desc.cpp

   1 //A -> (A)A | Epsilon
   2
   3 #include <iostream>
   4 #include <string>
   5
   6 using namespace std;
   7
   8 bool ok;
   9 char sgte;
  10 int i;
  11 string s;
  12
  13 bool match(char c){
  14   if (sgte != c){
  15     ok = false;
  16   }
  17   sgte = s[++i];
  18 }
  19
  20 void A(){
  21   if (sgte == '('){
  22     match('(');
  23     A(); match(')'); A();
  24   }else if (sgte == '$' || sgte == ')'){
  25     //nada
  26   }else{
  27     ok = false;
  28   }
  29 }
  30
  31 int main(){
  32   while(getline(cin, s) && s != ""){
  33     ok = true;
  34     s += '$';
  35     sgte = s[(i = 0)];
  36     A();
  37     if (i < s.length()-1) ok = false; //No consumi toda la cadena
  38     if (ok){
  39       cout << "Accepted\n";
  40     }else{
  41       cout << "Not accepted\n";
  42     }
  43
  44   }
  45 }