.S||“`

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using namespace std;

define endl ‘\n’

int n;
void printAllKLengthRec(char set[],string prefix)

if(prefix.length()==n)

cout<<prefix<<endl;
return;

for(int i=0;i<set.length();i++)

    string newPrefix;
    newPrefix=prefix+set[i];
    printAllKLengthRec(set,newPrefix);

void printAllKLength(char set[],int k)

n=k;
printAllKLengthRec(set,””);

int main()

char set[ ] = ‘a’,’b’;
int k = 3;
printAllKLength(set, k);

return 0;

1. **Header Includes and Macro Definitions**:

   - The code includes the necessary C++ Standard Library headers ( `<bits/stdc++.h>` ) for input/output and data structures.
   - It defines a macro, `endl`, to represent the end-of-line character, which is a platform-independent way of writing a newline.

2. **Global Variables**:

   - `n`: This integer variable will be used to store the desired length of the strings to be generated.

3. **Recursive Function: `printAllKLengthRec`**:

   - This recursive function is the core of the program. It takes the input character set (`set`) and a prefix string (`prefix`) as parameters.
   - It has a base case where it checks if the length of the `prefix` is equal to the desired length `n`. If so, it prints the `prefix` string on a new line, effectively representing a string of length `k` consisting of characters from the input `set`.
   - In the recursive case, it iterates through each character in the input `set`. For each character, it creates a new prefix by adding the character to the end of the current prefix. It then recursively calls itself with the updated `set` and `prefix`.

4. **Wrapper Function: `printAllKLength`**:

   - This function initializes the `n` variable with the desired string length `k` passed as an argument.
   - It initializes an empty prefix string (`""`) and calls the recursive function `printAllKLengthRec` with the input character `set` and the empty prefix.

5. **Main Function (`main`**:

   - In `main`, the program defines a sample character `set` as `'a', 'b'` and specifies a desired string length of `k = 3`.
   - It calls the `printAllKLength` function to generate and print all possible strings of length 3 using the characters in the `set`.

**Output for the Example**:

aaa
aab
aba
abb
baa
bab
bba
bbb

In this example, the program generates and prints all possible strings of length 3 that can be formed from the given character set `'a', 'b'`.

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