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Binary String of given length that without a palindrome of size 3
  • Difficulty Level : Medium
  • Last Updated : 18 Dec, 2019

Given an integer n. Find a string of characters ‘a’ and ‘b’ such that the string doesn’t contain any palindrome of length 3.

Examples:

Input : 3
Output : "aab"
Explanation:
aab is not a palindrome.

Input : 5
Output : aabba
Explanation:
aabba does not contain a palindrome
of size 3.

The approach here is that we can use this string ‘aabb’ and print the characters of the string according to the given integer.

We need to make make sure that every third 
character is different.

If we perform operation AND on i and 2 where
i = 0 to any positive integer. It will generate
a pattern 0, 0, 2, 2, 0, 0, 2, 2,... 
0 AND 2 = 0
1 AND 2 = 0
2 AND 2 = 2
3 AND 2 = 2
4 AND 2 = 0 //repeat the pattern.

Below is the code of above approach.

C++

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// CPP program find a binary string of 
// given length that doesn't contain
// a palindrome of size 3.
#include <bits/stdc++.h>
using namespace std;
  
void generatestring(int n)
{
    // Printing the character according to i
    for (int i = 0; i < n; i++)
        putchar(i & 2 ? 'b' : 'a');
    puts("");
}
  
// Driver code
int main()
{
    int n = 5;
    generatestring(n);
    n = 8;
    generatestring(n);
    n = 10;
    generatestring(n);
}

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Java

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// JAVA program find a binary String of 
// given length that doesn't contain
// a palindrome of size 3.
  
class GFG
{
  
static void generateString(int n)
{
    String s = "";
      
    // Printing the character according to i
    for (int i = 0; i < n; i++)
        s += ((i & 2) > 1 ? 'b' : 'a');
    System.out.println(s);
}
  
// Driver code
public static void main(String[] args)
{
    int n = 5;
    generateString(n);
    n = 8;
    generateString(n);
    n = 10;
    generateString(n);
}
}
  
// This code is contributed by Rajput-Ji

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Python3

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# Python3 program find a binary String of 
# given length that doesn't contain
# a palindrome of size 3.
def generateString(n):
    s = "";
      
    # Printing the character according to i
    for i in range(n):
        if((i & 2) > 1):
            s += 'b';
        else:
            s += 'a';
    print(s);
  
# Driver code
if __name__ == '__main__':
  
    n = 5;
    generateString(n);
    n = 8;
    generateString(n);
    n = 10;
    generateString(n);
  
# This code is contributed by 29AjayKumar

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C#

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// C# program find a binary String of 
// given length that doesn't contain
// a palindrome of size 3.
using System;
  
class GFG
{
  
static void generateString(int n)
{
    String s = "";
      
    // Printing the character according to i
    for (int i = 0; i < n; i++)
        s += ((i & 2) > 1 ? 'b' : 'a');
    Console.WriteLine(s);
}
  
// Driver code
public static void Main(String[] args)
{
    int n = 5;
    generateString(n);
    n = 8;
    generateString(n);
    n = 10;
    generateString(n);
}
}
  
// This code is contributed by Rajput-Ji

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Output:


aabba
aabbaabb
aabbaabbaa

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