Given 3 positive integers N, M, and K. the task is to construct a string of length N consisting of lowercase letters such that each substring of length M having exactly K distinct letters.
Examples:
Input: N = 5, M = 2, K = 2
Output: abade
Explanation:
Each substring of size 2 "ab", "ba", "ad", "de" have 2 distinct letters.
Input: N = 7, M = 5, K = 3
Output: abcaaab
Explanation:
Each substring of size 5 "tleel", "leelt", "eelte" have 3 distinct letters.
Approach: In a string of size N, every substring of size M must contain exactly K distinct letters-
- Construct a string having K distinct alphabets starting from 'a' to 'z' up to the size of M and put the rest of letters like 'a'..
- Since we have generated a string of size M with K distinct value. Now, keep repeating it till we reach string size of N.
Below is the implementation of the above approach:
// C++ program to generate a string of size N
// whose each substring of size M
// has exactly K distinct characters
#include <bits/stdc++.h>
using namespace std;
// Function to generate the string
string generateString(int N, int M, int K)
{
// Declare empty string
string s = "";
// counter for M
int cnt1 = 0;
// counter for K
int cnt2 = 0;
// Loop to generate string size of N
for (int i = 0; i < N; i++) {
cnt1++;
cnt2++;
// Generating K distinct
// letters one by one
if (cnt1 <= M) {
if (cnt2 <= K) {
s = s + char(96 + cnt1);
}
// After generating b distinct letters,
// append rest a-b letters as 'a'
else {
s = s + 'a';
}
}
// Reset the counter value
// and repeat the process
else {
cnt1 = 1;
cnt2 = 1;
s = s + 'a';
}
}
// return final result string
return s;
}
// Driver code
int main()
{
int N = 7, M = 5, K = 3;
cout << generateString(N, M, K) << endl;
return 0;
}
// Java program to generate a String of size N
// whose each subString of size M
// has exactly K distinct characters
import java.util.*;
class GFG{
// Function to generate the String
static String generateString(int N, int M, int K)
{
// Declare empty String
String s = "";
// counter for M
int cnt1 = 0;
// counter for K
int cnt2 = 0;
// Loop to generate String size of N
for (int i = 0; i < N; i++)
{
cnt1++;
cnt2++;
// Generating K distinct
// letters one by one
if (cnt1 <= M)
{
if (cnt2 <= K)
{
s = s + (char)(96 + cnt1);
}
// After generating b distinct letters,
// append rest a-b letters as 'a'
else
{
s = s + 'a';
}
}
// Reset the counter value
// and repeat the process
else
{
cnt1 = 1;
cnt2 = 1;
s = s + 'a';
}
}
// return final result String
return s;
}
// Driver code
public static void main(String[] args)
{
int N = 7, M = 5, K = 3;
System.out.println(generateString(N, M, K));
}
}
// This code is contributed by 29AjayKumar
# Python3 program to generate a string of size N
# whose each substring of size M
# has exactly K distinct characters
# Function to generate the string
def generateString(N, M, K):
# Declare empty string
s = ""
# counter for M
cnt1 = 0
# counter for K
cnt2 = 0
# Loop to generate string size of N
for i in range (N):
cnt1 += 1
cnt2 += 1
# Generating K distinct
# letters one by one
if (cnt1 <= M):
if (cnt2 <= K):
s = s + chr(96 + cnt1)
# After generating b distinct letters,
# append rest a-b letters as 'a'
else:
s = s + 'a'
# Reset the counter value
# and repeat the process
else:
cnt1 = 1
cnt2 = 1
s = s + 'a'
# return final result string
return s
# Driver code
if __name__ == "__main__":
N = 7
M = 5
K = 3
print (generateString(N, M, K))
# This code is contributed by Chitranayal
// C# program to generate a String of
// size N whose each subString of size
// M has exactly K distinct characters
using System;
class GFG{
// Function to generate the String
static String generateString(int N, int M, int K)
{
// Declare empty String
String s = "";
// Counter for M
int cnt1 = 0;
// Counter for K
int cnt2 = 0;
// Loop to generate String size of N
for(int i = 0; i < N; i++)
{
cnt1++;
cnt2++;
// Generating K distinct
// letters one by one
if (cnt1 <= M)
{
if (cnt2 <= K)
{
s = s + (char)(96 + cnt1);
}
// After generating b distinct letters,
// append rest a-b letters as 'a'
else
{
s = s + 'a';
}
}
// Reset the counter value
// and repeat the process
else
{
cnt1 = 1;
cnt2 = 1;
s = s + 'a';
}
}
// Return readonly result String
return s;
}
// Driver code
public static void Main(String[] args)
{
int N = 7, M = 5, K = 3;
Console.WriteLine(generateString(N, M, K));
}
}
// This code is contributed by Rajput-Ji
<script>
// Javascript program to generate
// a String of size N
// whose each subString of size M
// has exactly K distinct characters
// Function to generate the String
function generateString(N,M,K)
{
// Declare empty string
let s = "";
// counter for M
let cnt1 = 0;
// counter for K
let cnt2 = 0;
// Loop to generate string size of N
for (let i = 0; i < N; i++) {
cnt1++;
cnt2++;
// Generating K distinct
// letters one by one
if (cnt1 <= M) {
if (cnt2 <= K) {
s = s + String.fromCharCode(96 + cnt1);
}
// After generating b distinct letters,
// append rest a-b letters as 'a'
else {
s = s + 'a';
}
}
// Reset the counter value
// and repeat the process
else {
cnt1 = 1;
cnt2 = 1;
s = s + 'a';
}
}
// return final result string
return s;
}
// Driver code
let N = 7, M = 5, K = 3;
document.write( generateString(N, M, K))
// This code is contributed
// by avanitrachhadiya2155
</script>
Output
abcaaab
Time complexity: O(N)
Space complexity: O(1)
