Qt-interest Archive, August 2006
QMap<QString, ...> : optimized search...
Message 1 in thread
Hi all,
I would need to search a key in a QMap<QString, ...> in an optimized way,
knowing that the key to find is **most probably** after a given
QMap::iterator.
Question :
According to the efficiency tests I made, something like the "last accessed
iterator" is kept by the QMap. Consequently, searching for the key next to
the "last accessed iterator" is already optimized in Qt.
Is that right ?
In other words, for an optimized search, should I write something like :
----------------------------
QMap<QString, ...> myMap
// insert various elements
int aNumber = random(...) ;
QString searchedKey = QString().setNum(aNumber);
QMap<QString, ...>::iterator curItr = myMap.find( searchedKey );
if(curItr != m_namedLinks_M.end() {
// do smthing with the curItr ;
curItr ++ ;
}
// now searching for the key QString().setNum(aNumber + 1) ;
QString searchedKey = QString().setNum( aNumber + 1 );
if(curItr != m_namedLinks_M.end()
&& curItr.key() == searchedKey ) {
// check if the searchedKey is right after the latest search...
qDebug() << "next key found" ;
}
else {
curItr= m_namedLinks_M.constFind(searchedKey ) ;
if( curItr != m_namedLinks_M.end()) {
qDebug() << "next key found" ;
}
else {
qDebug() << "next key NOT found" ;
}
}
----------------------------
Or should I write more simply, with the same optimality :
----------------------------
QMap<QString, ...> myMap
// insert various elements
int aNumber = random(...) ;
QString searchedKey = QString().setNum(aNumber);
QMap<QString, ...>::iterator curItr = myMap.find( searchedKey );
if(curItr != m_namedLinks_M.end(){
// do smthing with the curItr ;
curItr ++ ;
}
// now searching for the key QString().setNum(aNumber + 1) ;
QString searchedKey = QString().setNum( aNumber + 1 );
curItr= m_namedLinks_M.constFind(searchedKey ) ;
if( curItr != m_namedLinks_M.end()) {
qDebug() << "next key found" ;
}
else {
qDebug() << "next key NOT found" ;
}
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[ signature omitted ]
