Cod sursa(job #184931)

Utilizator amadaeusLucian Boca amadaeus Data 24 aprilie 2008 15:49:35
Problema Evaluarea unei expresii Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.04 kb
#include <cstdio>
#include <cstring>

#define LMAX 2
char op[4][4] = { "+-", "*/", "^", "" };

#define NX 100010
char S[NX], *p = S;

struct node {
	int val;
	char op;
	node *l, *r;

	node( int a = 0, char b = 0, node *c = 0, node *d = 0 ) :
		val(a), op(b), l(c), r(d) {}
} *A;

node *expr( int lev ) {
	node *x, *y;
	
	if( lev == LMAX )
		if( *p == '(' )
			++p, x = expr(0), ++p;
		else
			for( x = new node; *p >= '0' && *p <= '9'; ++p )
				x->val = x->val * 10 + *p - '0';
	else
		for( x = expr( lev+1 ); strchr( op[lev], *p ); x = y )
			y = new node( 0, *p++, x, expr( lev+1 ) );
	return x;
}

int eval( node *n ) {
	switch( n->op ) {
		case '+': return eval( n->l ) + eval( n->r );
		case '-': return eval( n->l ) - eval( n->r );
		case '*': return eval( n->l ) * eval( n->r );
		case '/': return eval( n->l ) / eval( n->r );
		default: return n->val;
	}
}

int main() {
	fgets( S, NX, fopen( "evaluare.in", "r" ) );
	fprintf( fopen( "evaluare.out", "w" ), "%d\n", eval( A = expr(0) ) );

	return 0;
}