Print all possible strings of length k that can be formed from a set of n characters
Given a set of characters and a positive integer k, print all possible strings of length k that can be formed from the given set.
Examples:
Input: set[] = {'a', 'b'}, k = 3 Output: aaa aab aba abb baa bab bba bbb Input: set[] = {'a', 'b', 'c', 'd'}, k = 1 Output: a b c d
For a given set of size n, there will be n^k possible strings of length k. The idea is to start from an empty output string (we call it prefix in following code). One by one add all characters to prefix. For every character added, print all possible strings with current prefix by recursively calling for k equals to k1.
Following is Java implementation for same.

// Java program to print all possible strings of length k
class
PrintAllKLengthStrings {
// Driver method to test below methods
public
static
void
main(String[] args) {
System.out.println(
"First Test"
);
char
set1[] = {
'a'
,
'b'
};
int
k =
3
;
printAllKLength(set1, k);
System.out.println(
"\nSecond Test"
);
char
set2[] = {
'a'
,
'b'
,
'c'
,
'd'
};
k =
1
;
printAllKLength(set2, k);
}
// The method that prints all possible strings of length k. It is
// mainly a wrapper over recursive function printAllKLengthRec()
static
void
printAllKLength(
char
set[],
int
k) {
int
n = set.length;
printAllKLengthRec(set,
""
, n, k);
}
// The main recursive method to print all possible strings of length k
static
void
printAllKLengthRec(
char
set[], String prefix,
int
n,
int
k) {
// Base case: k is 0, print prefix
if
(k ==
0
) {
System.out.println(prefix);
return
;
}
// One by one add all characters from set and recursively
// call for k equals to k1
for
(
int
i =
0
; i < n; ++i) {
// Next character of input added
String newPrefix = prefix + set[i];
// k is decreased, because we have added a new character
printAllKLengthRec(set, newPrefix, n, k 
1
);
}
}
}
Output:
First Test aaa aab aba abb baa bab bba bbb Second Test a b c d
Disclaimer: This does not belong to TechCodeBit, its an article taken from the below
source and credits.
source and credits:http://www.geeksforgeeks.org/printallcombinationsofgivenlength/
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