给定一个长度为n的字符串，打印给定字符串的所有排列。允许重复字符。按字典顺序打印这些排列
例子：
Input: AB
Output: All permutations of AB with repetition are:
AA
AB
BA
BB
Input: ABC
Output: All permutations of ABC with repetition are:
AAA
AAB
AAC
ABA
...
...
CCB
CCC
对于大小为n的输入字符串，将存在n ^ n个允许重复的排列。这个想法是将第一个字符固定在第一个索引处，然后递归调用其他后续索引。一旦打印出从第一个字符开始的所有排列，就将第二个字符固定在第一个索引处。继续这些步骤，直到最后一个字符。感谢PsychoCoder提供了以下C实现。
C++
// C++ program to print all permutations
// with repetition of characters
#include
#include
using namespace std;
/* Following function is used by
the library qsort() function
to sort an array of chars */
int compare (const void * a, const void * b);
/* The main function that recursively
prints all repeated permutations of
the given string. It uses data[] to store all
permutations one by one */
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)
cout << data << endl;
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);
}
// Needed for library function qsort()
int compare (const void * a, const void * b)
{
return ( *(char *)a - *(char *)b );
}
// Driver code
int main()
{
char str[] = "ABC";
cout << "All permutations with repetition of "<<
str <<" are: "< C
// C program to print all permutations with repetition
// of characters
#include
#include
#include
/* Following function is used by the library qsort() function
to sort an array of chars */
int compare (const void * a, const void * b);
/* The main function that recursively prints all repeated
permutations of the given string. It uses data[] to store all
permutations one by one */
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 Java
// Java program to print all permutations
// with repetition of characters
import java.util.Arrays;
class GFG
{
// The main function that recursively prints
// all repeated permutations of the given string.
// It uses data[] to store all permutations one by one
static void allLexicographicRecur(String str, char[] data,
int last, int index)
{
int length = str.length();
// One by one fix all characters at the given index
// and recur for the subsequent indexes
for (int i = 0; i < length; i++)
{
// Fix the ith character at index and if
// this is not the last index then
// recursively call for higher indexes
data[index] = str.charAt(i);
// If this is the last index then print
// the string stored in data[]
if (index == last)
System.out.println(new String(data));
else
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
static void allLexicographic(String str)
{
int length = str.length();
// Create a temp array that will be used by
// allLexicographicRecur()
char[] data = new char[length + 1];
char[] temp = str.toCharArray();
// Sort the input string so that we get all
// output strings in lexicographically sorted order
Arrays.sort(temp);
str = new String(temp);
// Now print all permutaions
allLexicographicRecur(str, data, length - 1, 0);
}
// Driver Code
public static void main(String[] args)
{
String str = "ABC";
System.out.printf("All permutations with " +
"repetition of %s are: \n", str);
allLexicographic(str);
}
}
// This code is contributed by
// sanjeev2552Python
# Python program to print all permutations with repetition
# of characters
def toString(List):
return ''.join(List)
# The main function that recursively prints all repeated
# permutations of the given string. It uses data[] to store
# all permutations one by one
def allLexicographicRecur (string, data, last, index):
length = len(string)
# One by one fix all characters at the given index and
# recur for the subsequent indexes
for i in xrange(length):
# Fix the ith character at index and if this is not
# the last index then recursively call for higher
# indexes
data[index] = string[i]
# If this is the last index then print the string
# stored in data[]
if index==last:
print toString(data)
else:
allLexicographicRecur(string, data, last, index+1)
# This function sorts input string, allocate memory for data
# (needed for allLexicographicRecur()) and calls
# allLexicographicRecur() for printing all permutations
def allLexicographic(string):
length = len(string)
# Create a temp array that will be used by
# allLexicographicRecur()
data = [""] * (length+1)
# Sort the input string so that we get all output strings in
# lexicographically sorted order
string = sorted(string)
# Now print all permutaions
allLexicographicRecur(string, data, length-1, 0)
# Driver program to test the above functions
string = "ABC"
print "All permutations with repetition of " + string + " are:"
allLexicographic(string)
# This code is contributed to Bhavya JainC#
// C# program to print all permutations
// with repetition of characters
using System;
public class GFG
{
// The main function that recursively prints
// all repeated permutations of the given string.
// It uses data[] to store all permutations one by one
static void allLexicographicRecur(String str, char[] data,
int last, int index)
{
int length = str.Length;
// One by one fix all characters at the given index
// and recur for the subsequent indexes
for (int i = 0; i < length; 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)
Console.WriteLine(new String(data));
else
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
static void allLexicographic(String str)
{
int length = str.Length;
// Create a temp array that will be used by
// allLexicographicRecur()
char[] data = new char[length + 1];
char[] temp = str.ToCharArray();
// Sort the input string so that we get all
// output strings in lexicographically sorted order
Array.Sort(temp);
str = new String(temp);
// Now print all permutaions
allLexicographicRecur(str, data, length - 1, 0);
}
// Driver Code
public static void Main(String[] args)
{
String str = "ABC";
Console.Write("All permutations with " +
"repetition of {0} are: \n", str);
allLexicographic(str);
}
}
// This code is contributed by PrinciRaj1992输出：
All permutations with repetition of ABC are:
AAA
AAB
AAC
ABA
ABB
ABC
ACA
ACB
ACC
BAA
BAB
BAC
BBA
BBB
BBC
BCA
BCB
BCC
CAA
CAB
CAC
CBA
CBB
CBC
CCA
CCB
CCC
C语言编程基础
GeeksforGeeks的免费在线课程
以下是输入字符串“ AB”的递归树。递归树的目的是帮助理解上面的实现，因为它显示了不同变量的值。
data=""
/ \
/ \
index=0 index=0
i=0 i=1
data="A" data="B"
/ \ / \
/ \ / \
index=1 index=1 index=1 index=1
i=0 i=1 i=0 i=1
data="AA" data="AB" data="BA" data="BB"
在上面的实现中，假设输入字符串的所有字符都不同。该实现可以轻松修改以处理重复的字符。我们必须添加一个预处理步骤来查找唯一字符(在调用allLexicographicRecur()之前)。