Check if Binary Array can be made Palindrome by flipping two bits at a time

Given a binary array A[] of size N, the task is to check whether the array can be converted into a palindrome by flipping two bits in each operation.

Note: The operation can be performed any number of times.

Examples:

Input: A[] = {1, 0, 1, 0, 1, 1}
Output: Yes
?Explanation: We can perform the following operation:
Select i = 2 and j = 4. Then {1, 0, 1, 0, 1, 1}?{1, 0, 0, 0, 0, 1} which is a palindrome.

Input: A[] = {0, 1}
Output: No

Approach: The problem can be solved based on the following observation: 

Count number of 0s and 1s. 

• If the value of count of 0s and 1s are odd then no palindrome can be made by performing operation on A[].
• Otherwise, array A[] can converted into a palindrome after performing operation on array.

Follow the below steps to solve the problem:

• Set zeros = 0 and ones = 0 to store the count of number of 0s and 1s in the array.
• After that iterate a loop from 0 to N-1 such as:
  • If A[i] = 0 increment the value of zeros otherwise increment the value of ones.
• If the value of zeros and ones is odd then print “No” i.e. it is not possible to convert A to a palindrome by applying the above operation any number of times.
• Otherwise, print “Yes”.

Below is the implementation of the above approach.

C++

// C++ code to implement the approach
#include <bits/stdc++.h>
using namespace std;

// Function to find check whether
// array can converted into palindrome
string check(int arr[], int n)
{
    int one = 0, zero = 0;
    for (int i = 0; i < n; i++) {
        if (arr[i] == '0') {
            zero++;
        }
        else {
            one++;
        }
    }
    if (one % 2 != 0 && zero % 2 != 0)
        return "No";
    return "Yes";
}

// Driver Code
int main()
{
    int A[] = { 1, 0, 1, 0, 1, 1 };
    int N = sizeof(A) / sizeof(A[0]);

    // Function call
    cout << check(A, N);

    return 0;
}

// This code is contributed by aarohirai2616.

Java

// Java code to implement the approach

import java.io.*;
import java.util.*;

public class GFG {

    // Function to find check whether
    // array can converted into palindrome
    public static String check(int arr[], int n)
    {
        int one = 0, zero = 0;
        for (int i = 0; i < n; i++) {
            if (arr[i] == '0') {
                zero++;
            }
            else {
                one++;
            }
        }
        if (one % 2 != 0 && zero % 2 != 0)
            return "No";
        return "Yes";
    }

    // Driver Code
    public static void main(String[] args)
    {
        int[] A = { 1, 0, 1, 0, 1, 1 };
        int N = A.length;

        // Function Call
        System.out.println(check(A, N));
    }
}

Python3

# Python code to implement the approach

# Function to find check whether
# array can converted into palindrome
def check(arr, n):
    one = 0
    zero = 0
    for i in range(0, n):
            if (arr[i] == '0'):
                zero = zero + 1

            else:
                one = one + 1

    if(one % 2 != 0 & zero % 2 != 0):
            return "No"
    return "Yes"

# Driver Code
if __name__ == '__main__':
    A = [1, 0, 1, 0, 1, 1 ]
    N = len(A)

    # Function call
    print(check(A,N))

    # This code is contributed by aarohirai2616.

C#

using System;
class GFG {
  static string check(int[] arr, int n)
  {
    int one = 0, zero = 0;
    for (int i = 0; i < n; i++) {
      if (arr[i] == '0') {
        zero++;
      }
      else {
        one++;
      }
    }
    if (one % 2 != 0 && zero % 2 != 0)
      return "No";
    return "Yes";
  }
  static void Main()
  {
    int[] A = { 1, 0, 1, 0, 1, 1 };
    int N = 6;

    // Function Call
    Console.Write(check(A, N));
  }
}

// This code is contributed by garg28harsh.

Javascript

// JavaScript code to implement the approach

// Function to find check whether
// array can converted into palindrome
const check = (arr, n) => {
    let one = 0, zero = 0;
    for (let i = 0; i < n; i++) {
        if (arr[i] == '0') {
            zero++;
        }
        else {
            one++;
        }
    }
    if (one % 2 != 0 && zero % 2 != 0)
        return "No";
    return "Yes";
}

// Driver Code
let A = [1, 0, 1, 0, 1, 1];
let N = A.length;

// Function call
console.log(check(A, N));

// This code is contributed by rakeshsahni

Output

Yes

Time Complexity: O(N)
Auxiliary Space: O(1)

Another Approach:

1. Start the program.
2. Declare the canBePalindrome() function that takes an integer array arr and its size n as arguments and returns a boolean value.
3. Inside the canBePalindrome() function, initialize two integer variables count0 and count1 to 0 to keep the count of 0s and 1s in the array.
4. Use a for loop to iterate through each element of the array arr.
5. Check if the current element of arr is 0 using the if statement. If it is, increment the value of count0 by 1, else increment the value of count1 by 1.
6. After the loop, check if the count of 0s and count of 1s in the array are both even using the boolean expression count0 % 2 == 0 && count1 % 2 == 0. If they are both even, return true, else return false.
7. In the main() function, declare an integer array arr and initialize it with the given values.
8. Find the size of the array arr using the expression sizeof(arr) / sizeof(arr[0]) and store it in an integer variable n.
9. Call the canBePalindrome() function with the array arr and its size n as arguments.
10. Use an if-else statement to check if the returned value from canBePalindrome() is true or false. If it is true, print “Yes”, else print “No”.
11. End the program.

C++

#include <iostream>
using namespace std;

bool canBePalindrome(int arr[], int n) {
    int count0 = 0, count1 = 0;
    for (int i = 0; i < n; i++) {
        if (arr[i] == 0) count0++;
        else count1++;
    }
    return (count0 % 2 == 0 && count1 % 2 == 0);
}

int main() {
    int arr[] = {1, 0, 1, 0, 1, 1};
    int n = sizeof(arr) / sizeof(arr[0]);

    if (canBePalindrome(arr, n)) cout << "Yes";
    else cout << "No";

    return 0;
}

Java

import java.io.*;

public class Main {

    public static boolean canBePalindrome(int[] arr) {

        int count0 = 0, count1 = 0;

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

            if (arr[i] == 0) count0++;

            else count1++;

        }

        return (count0 % 2 == 0 && count1 % 2 == 0);

    }

    public static void main(String[] args) {

        int[] arr = {1, 0, 1, 0, 1, 1};

        if (canBePalindrome(arr)) System.out.println("Yes");

        else System.out.println("No");

    }

}

Python3

# Python3 program for the above approach
def can_be_palindrome(arr):
    count_0 = 0
    count_1 = 0
    for num in arr:
        if num == 0:
            count_0 += 1
        else:
            count_1 += 1
    return count_0 % 2 == 0 and count_1 % 2 == 0


# Driver Code
arr = [1, 0, 1, 0, 1, 1]
n = len(arr)

if can_be_palindrome(arr):
    print("Yes")
else:
    print("No")

C#

using System;

public class Program {
    public static bool CanBePalindrome(int[] arr, int n) {
        int count0 = 0, count1 = 0;
        for (int i = 0; i < n; i++) {
            if (arr[i] == 0) count0++;
            else count1++;
        }
        return (count0 % 2 == 0 && count1 % 2 == 0);
    }

    public static void Main() {
        int[] arr = {1, 0, 1, 0, 1, 1};
        int n = arr.Length;

        if (CanBePalindrome(arr, n)) Console.WriteLine("Yes");
        else Console.WriteLine("No");
    }
}

Javascript

function canBePalindrome(arr) {
    let count0 = 0, count1 = 0;
    for (let i = 0; i < arr.length; i++) {
        if (arr[i] === 0) count0++;
        else count1++;
    }
    return (count0 % 2 === 0 && count1 % 2 === 0);
}

const arr = [1, 0, 1, 0, 1, 1];
const result = canBePalindrome(arr);

if (result) {
    console.log("Yes");
} else {
    console.log("No");
}

//This code is written by Ujjwal Kumar Bhardwaj

Output

Yes

Time Complexity: O(N)
Auxiliary Complexity: O(1)