Anagrams with regular expression

  • Hi all,
    What is the regular expression that represents all of anagrams of a string.
    For example:
    input string: "abc"
    output strings: "bca", "abc", "bac" ...

    This regular expression will be used with a QSortFilterProxyModel to display anagrams of a given string.

  • You want to use the regular expression to test strings or to generate strings? If you need to generate,
    you don't need a regular expression. You will have to write a code which generate all permutations from
    1 to input.length(), and use each permutation to create a new string.

    Anyway try this. the idea comes from creating the occurrence map. I let you test it properly:


    #include <QtCore/QCoreApplication>
    #include <QMap>
    #include <QList>
    #include <iostream>
    #include <QRegExp>

    using namespace std;

    QString anagramRegexGenerator(const QString &input);

    int main(int argc, char *argv[])
    QCoreApplication a(argc, argv);

    const QString s = "anagrams";
    QList<QString> list;
    list << "aangrams"
         << "granamas"
         << "anagrams"
         << "ngrmsaaa"
         << "magarans"
         << "an ag rams";// shound not passs
    QString regstring = anagramRegexGenerator(s);
    cout << " I found the expression :" << regstring.toStdString() <<endl;
    QRegExp regexp(regstring);
        QString yes = "matches";
        QString no = "doesn't match";
        for(int i = 0; i < list.size(); i++){
            QString output;
                output = yes;
                output = no;
            cout << list[i].toStdString()<<" "<<output.toStdString()<<" the regular expression" <<endl;
    return a.exec&#40;&#41;;


    /** count the occurences of each character,

    • and create a string valid regex.
      QString anagramRegexGenerator(const QString &input){
      QString lookaheadPart = "";
      QString matchingPart = "^";
      const QString positiveLookaheadPrefix="(?=";
      const QString positiveLookaheadSuffix=")";
      QMap<QChar,int> inputCharacterFrequencyMap;

      for ( int i = 0; i< input.length(); i++ )
      if (!inputCharacterFrequencyMap.contains(input[i])) {
      inputCharacterFrequencyMap[input[i]] = 1;
      } else {
      foreach(const QChar car,inputCharacterFrequencyMap.keys() ){
      lookaheadPart += positiveLookaheadPrefix;
      for (int k = 0; k< inputCharacterFrequencyMap[car]; k++) {
      lookaheadPart += ".*";
      if (car == ' ') {
      lookaheadPart += "\s";
      } else {
      lookaheadPart += car;
      matchingPart += ".";
      lookaheadPart += positiveLookaheadSuffix;
      matchingPart += "$";
      return lookaheadPart + matchingPart;


  • I want filter a QSortFilterProxyModel, i.e. retrieve items that are anagrams of a given string.

  • Look at "this algorithm...":

    You need to sort the characters in the string (anagram becomes aaagmrn), and apply it.
    Best of luck.

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