itertools.permutations(iterable[, r])

This tool returns successive $\textbf{r}$ length permutations of elements in an iterable.

If $\textbf{r}$ is not specified or is None, then $\textbf{r}$ defaults to the length of the iterable, and all possible full length permutations are generated.

Permutations are printed in a lexicographic sorted order. So, if the input iterable is sorted, the permutation tuples will be produced in a sorted order.

Sample Code

from itertools import permutations
print permutations(['1','2','3'])
<itertools.permutations object at 0x02A45210>

print list(permutations(['1','2','3']))
[('1', '2', '3'), ('1', '3', '2'), ('2', '1', '3'), ('2', '3', '1'), ('3', '1', '2'), ('3', '2', '1')]

print list(permutations(['1','2','3'],2))
[('1', '2'), ('1', '3'), ('2', '1'), ('2', '3'), ('3', '1'), ('3', '2')]

print list(permutations('abc',3))
[('a', 'b', 'c'), ('a', 'c', 'b'), ('b', 'a', 'c'), ('b', 'c', 'a'), ('c', 'a', 'b'), ('c', 'b', 'a')]

Task

You are given a string $\mbox{S}$.

Your task is to print all possible permutations of size $\boldsymbol{\mbox{k}}$ of the string in lexicographic sorted order.

Input Format

A single line containing the space separated string $\mbox{S}$ and the integer value $\boldsymbol{\mbox{k}}$.

Constraints

$0<k\leq len(S)$

The string contains only UPPERCASE characters.

Output Format

Print the permutations of the string $\mbox{S}$ on separate lines.

Sample Input
HACK 2

Sample Output
AC
AH
AK
CA
CH
CK
HA
HC
HK
KA
KC
KH

Explanation

All possible size $2$ permutations of the string "HACK" are printed in lexicographic sorted order.

见题面

见题面