Print all permutations with repetition of characters | GeeksforGeeks

Given a string of length n, print all permutation of the given string. Repetition of characters is allowed. Print these permutations in lexicographically sorted order 
Examples:

Input: AB
Ouput: All permutations of AB with repetition are:
      AA
      AB
      BA
      BB

void allLexicographicRecur (char *str, char* data, int last, int index)

{

    int i, len = strlen(str);

    // One by one fix all characters at the given index and recur for the

    // subsequent indexes

    for ( i=0; i<len; i++ )

    {

        // Fix the ith character at index and if this is not the last index

        // then recursively call for higher indexes

        data[index] = str[i] ;

        // If this is the last index then print the string stored in data[]

        if (index == last)

            printf("%s\n", data);

        else // Recur for higher indexes

            allLexicographicRecur (str, data, last, index+1);

    }

}

/* This function sorts input string, allocate memory for data (needed for

  allLexicographicRecur()) and calls allLexicographicRecur() for printing all

  permutations */

void allLexicographic(char *str)

{

    int len = strlen (str) ;

 

    // Create a temp array that will be used by allLexicographicRecur()

    char *data = (char *) malloc (sizeof(char) * (len + 1)) ;

    data[len] = '\0';

    // Sort the input string so that we get all output strings in

    // lexicographically sorted order

    qsort(str, len, sizeof(char), compare);

    // Now print all permutaions

    allLexicographicRecur (str, data, len-1, 0);

    // Free data to avoid memory leak

    free(data);

}

In the above implementation, it is assumed that all characters of the input string are different. The implementation can be easily modified to handle the repeated characters. We have to add a preprocessing step to find unique characters (before calling allLexicographicRecur()).

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