打印具有重复项的给定字符串的所有不同排列

给定一个可能包含重复项的字符串，编写一个函数以打印给定字符串的所有排列，以使输出中不重复排列。

例子：

Input:  str[] = "AB"
Output: AB BA

Input:  str[] = "AA"
Output: AA

Input:  str[] = "ABC"
Output: ABC ACB BAC BCA CBA CAB

Input:  str[] = "ABA"
Output: ABA AAB BAA

Input:  str[] = "ABCA"
Output: AABC AACB ABAC ABCA ACBA ACAB BAAC BACA 
        BCAA CABA CAAB CBAA

我们在下面的文章中讨论了打印所有排列的算法。强烈建议将以下帖子作为此帖子的先决条件。

编写C程序以打印给定字符串的所有排列

上面链接中讨论的算法不能处理重复项。

// Program to print all permutations of a
// string in sorted order.
#include 
#include 
#include 
  
/* Following function is needed for library
  function qsort(). */
int compare(const void* a, const void* b)
{
    return (*(char*)a - *(char*)b);
}
  
// A utility function two swap two characters
// a and b
void swap(char* a, char* b)
{
    char t = *a;
    *a = *b;
    *b = t;
}
  
// This function finds the index of the
// smallest character which is greater
// than 'first' and is present in str[l..h]
int findCeil(char str[], char first, int l, int h)
{
    // initialize index of ceiling element
    int ceilIndex = l;
  
    // Now iterate through rest of the
    // elements and find the smallest
    // character greater than 'first'
    for (int i = l + 1; i <= h; i++)
        if (str[i] > first && str[i] < str[ceilIndex])
            ceilIndex = i;
  
    return ceilIndex;
}
  
// Print all permutations of str in sorted order
void sortedPermutations(char str[])
{
    // Get size of string
    int size = strlen(str);
  
    // Sort the string in increasing order
    qsort(str, size, sizeof(str[0]), compare);
  
    // Print permutations one by one
    bool isFinished = false;
    while (!isFinished) {
  
        // print this permutation
        static int x = 1;
        printf("%d  %s \n", x++, str);
  
        // Find the rightmost character
        // which is smaller than its next
        // character. Let us call it 'first
        // char'
        int i;
        for (i = size - 2; i >= 0; --i)
            if (str[i] < str[i + 1])
                break;
  
        // If there is no such character, all
        // are sorted in decreasing order,
        // means we just printed the last
        // permutation and we are done.
        if (i == -1)
            isFinished = true;
        else {
  
            // Find the ceil of 'first char'
            // in right of first character.
            // Ceil of a character is the
            // smallest character greater
            // than it
            int ceilIndex = findCeil(str,
                     str[i], i + 1, size - 1);
  
            // Swap first and second characters
            swap(&str[i], &str[ceilIndex]);
  
            // Sort the string on right of 'first char'
            qsort(str + i + 1, size - i - 1,
                  sizeof(str[0]), compare);
        }
    }
}
  
// Driver program to test above function
int main()
{
    char str[] = "ACBC";
    sortedPermutations(str);
    return 0;
}

输出：

1  ABCC
2  ACBC
3  ACCB
4  BACC
5  BCAC
6  BCCA
7  CABC
8  CACB
9  CBAC
10  CBCA
11  CCAB
12  CCBA

上面的代码摘自Lazy先生在下面的评论中。

时间复杂度：O(n ² * n！)
辅助空间：O(1)