pop method
dynamic
pop()
Returns the item with the highest priority and removes it from the priority queue.
Implementation
pop() {
if ( length == 0 ) return null;
final top = data[ 0 ];
length --;
if ( length > 0 ) {
data[ 0 ] = data[ length ];
_down( 0 );
}
data.removeLast();
return top;
}