Given a positive integer K, the task is to find lexicographically the smallest string that can be generated by using the first K lowercase alphabets such that no substring of length at least 2 is repeated in the generated string.
Examples:
Input: K = 3
Output: aabacbbcca
Explanation:
In the string “aabacbbcca”, all possible substrings of length at least 2 is repeated more than once.Input: K = 4
Output: aabacadbbcbdccdda
Approach: The given problem can be solved based on the following observations:
- If all substrings of length 2 are unique, then all substrings of length greater than 2 will also be unique.
- Hence, the maximum length string should contain all unique substrings of length 2 arrange in lexicographic order such that no 3 consecutive characters in the string are the same.
Follow the steps below to solve the problem:
- Initialize a string, say S as the empty string that stores the resultant string.
- Iterate over all the first K characters of the lowercase alphabet using the variable, say i and perform the following steps:
- Append the current character i to the string S.
- Iterate from the (i + 1)th character to the Kth character, and append the character i followed by character j to the string S.
- Add the character ‘a’ to the string S so that substring consisting of the last and the first alphabet is also present in the resultant string.
- After completing the above steps, print the string S as the resultant string.
Below is the implementation of the above approach:
// C++ program for the above approach #include <bits/stdc++.h> using namespace std;
// Function to find the lexicographically // smallest string of the first K lower // case alphabets having unique substrings void generateString( int K)
{ // Stores the resultant string
string s = "" ;
// Iterate through all the characters
for ( int i = 97; i < 97 + K; i++) {
s = s + char (i);
// Inner Loop for making pairs
// and adding them into string
for ( int j = i + 1;
j < 97 + K; j++) {
s += char (i);
s += char (j);
}
}
// Adding first character so that
// substring consisting of the last
// the first alphabet is present
s += char (97);
// Print the resultant string
cout << s;
} // Driver Code int main()
{ int K = 4;
generateString(K);
return 0;
} |
// Java program for the above approach import java.util.*;
class GFG{
// Function to find the lexicographically // smallest string of the first K lower // case alphabets having unique substrings static void generateString( int K)
{ // Stores the resultant string
String s = "" ;
// Iterate through all the characters
for ( int i = 97 ; i < 97 + K; i++)
{
s = s + ( char )(i);
// Inner Loop for making pairs
// and adding them into string
for ( int j = i + 1 ; j < 97 + K; j++)
{
s += ( char )(i);
s += ( char )(j);
}
}
// Adding first character so that
// substring consisting of the last
// the first alphabet is present
s += ( char )( 97 );
// Print the resultant string
System.out.println(s);
} // Driver code public static void main(String []args)
{ int K = 4 ;
generateString(K);
} } // This code is contributed by sanjoy_62 |
// C# program for the above approach using System;
class GFG{
// Function to find the lexicographically // smallest string of the first K lower // case alphabets having unique substrings static void generateString( int K)
{ // Stores the resultant string
string s = "" ;
// Iterate through all the characters
for ( int i = 97; i < 97 + K; i++)
{
s = s + ( char )(i);
// Inner Loop for making pairs
// and adding them into string
for ( int j = i + 1; j < 97 + K; j++)
{
s += ( char )(i);
s += ( char )(j);
}
}
// Adding first character so that
// substring consisting of the last
// the first alphabet is present
s += ( char )(97);
// Print the resultant string
Console.Write(s);
} // Driver Code public static void Main()
{ int K = 4;
generateString(K);
} } // This code is contributed by ukasp |
# python 3 program for the above approach # Function to find the lexicographically # smallest string of the first K lower # case alphabets having unique substrings def generateString(K):
# Stores the resultant string
s = ""
# Iterate through all the characters
for i in range ( 97 , 97 + K, 1 ):
s = s + chr (i);
# Inner Loop for making pairs
# and adding them into string
for j in range (i + 1 , 97 + K, 1 ):
s + = chr (i)
s + = chr (j)
# Adding first character so that
# substring consisting of the last
# the first alphabet is present
s + = chr ( 97 )
# Print the resultant string
print (s)
# Driver Code if __name__ = = '__main__' :
K = 4
generateString(K)
# This code is contributed by SURENDRA_GANGWAR.
|
<script> // JavaScript program for the above approach // Function to find the lexicographically // smallest string of the first K lower // case alphabets having unique substrings function generateString(K)
{ // Stores the resultant string
var s = "" ;
// Iterate through all the characters
for ( var i = 97; i < 97 + K; i++)
{
s = s + String.fromCharCode(i);
// Inner Loop for making pairs
// and adding them into string
for ( var j = i + 1; j < 97 + K; j++)
{
s += String.fromCharCode(i);
s += String.fromCharCode(j);
}
}
// Adding first character so that
// substring consisting of the last
// the first alphabet is present
s += String.fromCharCode(97);
// Print the resultant string
document.write(s);
} // Driver code var K = 4;
generateString(K); // This code is contributed by 29AjayKumar </script> |
aabacadbbcbdccdda
Time Complexity: O(K2)
Auxiliary Space: O(K2)