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)