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Cod sursa(job #184919)
#include <cstdio>
#include <cstring>
#define LMAX 2
char op[4][4] = { "+-", "*/", "^", "" };
#define NX (1<<17)
char S[ NX ], *p;
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;
int parse() {
int x;
for( x=0; *p >= '0' && *p <= '9'; ++p )
x = x*10 + *p - '0';
return x;
}
node *expr( int lev ) {
node *x, *y;
if( lev == LMAX )
if( *p == '(' )
++p, x = expr(0), ++p;
else
x = new node( parse() );
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() {
freopen( "evaluare.in", "r", stdin );
freopen( "evaluare.out", "w", stdout );
fgets( S, NX, stdin ), p = S;
A = expr( 0 );
printf( "%d\n", eval( A ) );
return 0;
}