Cod sursa(job #581638)

Utilizator BitOneSAlexandru BitOne Data 14 aprilie 2011 14:20:53
Problema Evaluarea unei expresii Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.1 kb
#include <string>
#include <fstream>
#include <cstdlib>

using namespace std;
string exp;
string::const_iterator it, iend;
const string op[]={ "+-", "*/", "^" };
inline int eval( int a, int b, char op )
{
    switch( op )
    {
        case '+' : return a+b;
        case '-' : return a-b;
        case '*' : return a*b;
        case '/' : return a/b;
        default : exit(1);
    }
}
inline int eval( int level )
{
    int x=0;
    if( 2 == level )
    {
        if( '(' == *it )
        {
            ++it;
            x=eval(0);
            ++it;
        }
        else for( x=0; it < iend && *it >= '0' && *it <= '9'; ++it )
                x=x*10+*it-'0';
    }
    else for( x=eval(level+1); it < iend && string::npos != op[level].find(*it);  )
         {
             char op=*it;
             ++it;
             x=eval( x, eval(1+level), op );
         }
    return x;
}
int main( void )
{
    ifstream in( "evaluare.in" );
    getline( in, exp );
    it=exp.begin(), iend=exp.end();
    ofstream out( "evaluare.out" );
    out<<eval(0)<<'\n';
    return EXIT_SUCCESS;
}