Find the Longest Palindrome in an Array using Python

June 2, 2022

Longest Palindrome in an Array

Here, in this page we will discuss the program to find the longest palindrome in an array in python programming language, we will discuss two different methods to find the longest palindromic element in the given array.

Here in this page we will discuss the following methods to find the longest palindromic number.

Method 1 : Using Naive Approach
Method 2 : Using Sorting

Method 1 :

Create a function ispalindrome(int n), it will return 1 if the passing number is palindrome otherwise return 0.
Inside the main function, create a variable say res = -1, that hold the maximum palindrome number.
Run a loop from [0, n), and check if(ispalindrome(arr[i]) && res<arr[i]), then set res = arr[i].
Print the value of res.

Method 1 : Code in Python

Run

# Function to check if n is palindrome
def isPalindrome(n):

   divisor = 1
   while (int(n / divisor) >= 10):
      divisor *= 10

   while (n != 0):
      leading = int(n / divisor)
      trailing = n % 10
  
      if (leading != trailing):
        return False

      n = int((n % divisor) / 10)

      divisor = int(divisor / 100)
   return True

# Function to find the largest palindromic element
def largestPalindrome(arr, n):
   currentMax = -1

   for i in range(0, n, 1):
      if (arr[i] > currentMax and isPalindrome(arr[i])):
         currentMax = arr[i]

   return currentMax

# Driver Code

arr = [1, 232, 5545455, 909090, 161]
n = len(arr)

# print required answer
print(largestPalindrome(arr, n))

Output

Method 2 :

In this method we first sort the array and then start traversing the array from end, and return the element that satisfy the condition, that it is palindrome.

Sort the array using inbuilt sort() function.
Start traversing from end of the array,
Print the element if it is palindrome.
If no element found then print -1.

About sort() function in Python

The sort() method is a built-in Python method that, by default, sorts the list in ascending order.
However, you can modify the order from ascending to descending by specifying the sorting criteria.
array_name.sort(reverse=True|False, key=myFunc) , this will sort the array in descending order.

Method 2 : Code in Python

Run

# Function to check if n is palindrome
def isPalindrome(n):

   divisor = 1
   while (int(n / divisor) >= 10):
      divisor *= 10

   while (n != 0):
      leading = int(n / divisor)
      trailing = n % 10
  
      if (leading != trailing):
        return False

      n = int((n % divisor) / 10)

      divisor = int(divisor / 100)
   return True

# Function to find the largest palindromic element
def largestPalindrome(A, n) :
    # Sort the array
    A.sort()

    for i in range(n - 1, -1, -1) :
        # If number is palindrome
        if (isPalindrome(A[i])) :
            return A[i]    

    # If no palindromic number found
    return -1

# Driver Code 
arr = [1, 232, 5545455, 909090, 161]
n = len(arr) 
# print required answer 
print(largestPalindrome(arr, n))

Output

8 comments on “Find the Longest Palindrome in an Array using Python”

Sanjeet
//Try this in C: Longest palindrome in array
#include
int main()
{
int arr[100],n,i,j,l_pallindrome=0;
printf(“Enter the size of array: “);
scanf(“%d”,&n);
for(i=0;i<n;i++)
{
scanf("%d",&arr[i]);
}
for(i=0;i0)
{
rem=temp%10;
rev=rev*10+rem;
temp=temp/10;
}
if(arr[i]==rev)
{
if(rev>l_pallindrome)
{
l_pallindrome=rev;
}
}
}
printf(“The longest palindrome in array : %d”,l_pallindrome);
return 0;
}

0

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Bibhudutta
n=int(input())
arr=list()
arr1=list()
for i in range(0,n):
arr.append(int(input()))

for i in arr:
temp=i
rev=0
while(temp>0):
rem=temp%10
rev=rev*10+rem
temp=temp//10
if(i==rev):
arr1.append(rev)

print(‘maximum element is -‘,max(arr1))

1

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Mayuresh
arr = list(map(int,input().split())

a = []

flag = True

for i in arr:
if(str(i) == str(i)[::-1]):
a.append(i)
flag = False
if(flag):
print(“no palindromic number in array”)
else:
print(max(a))

0

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Nikita
def is_palindrome(ele):
temp = ele
reverse = 0
while temp > 0:
rem = temp % 10
reverse = reverse * 10 + rem
temp = temp // 10
if reverse == ele:
return digits(ele)
else:
return 0

def digits(ele):
n = ele
count = 0
while n > 0:
rem = n % 10
count += 1
n = n // 10
return count

arr = [1210, 11211, 1112111, 141, 11411]
list = []
for i in range(len(arr)):
list.append(is_palindrome(arr[i]))

def largest(list):
largest_ele = list[0]
for i in range(len(list)):
if largest_ele < list[i]:
largest_ele = list[i]
for i in list:
if largest_ele == list[i]:
return print(f"{arr[i]} is the longest palindrome with {largest_ele} digits")
largest(list)

0

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Tirtham
s=int(input())

lst=[]
arr=[]
a=0
for i in range(0,s,1):
n=int(input())
lst.append(n)
for j in lst:
if str(j)== str(j) [::-1]:
arr.append(j)
arr.sort()
l=len(arr)
print(arr[l-1])

0

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Arun
#A number is 526625 .If you read number “526625” from reverse order,
# it is same as “526625”.
from array import *
a= int(input(“enter the number of input :”))
b=array(“i”,[])
for x in range(a):
b1=int(input((“Enter a value :”)))
b.append(b1)
m=[]
for x in range(a):
c1=str(b[x])
if c1 == c1[::-1]:
m.append(c1)
print(max(m))

0

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Shaik
n=int(input())
l=[]
for i in range(n):
l.append(int(input()))
l.sort(reverse=True)
for x in l:
if str(x)==str(x)[::-1]:
print(‘longest palindrome’,x)
break
else:
print(‘no’)

0

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Pradeep
//Longest Palindrome in an Array in C language

#include
int palindrome(int);
void main()
{

int i, n,count=0,s,c=0;
printf(“Enter the size of array:”);
scanf(“%d”,&n);
int a[n];
for(i=0;i<n;i++)
{
printf("element – %d : ",i);
scanf("%d",&a[i]);
}
int p[20];
int j;
for(i=0,j=0;i<n;i++)
{
int result=palindrome(a[i]);
if(result==1)
{
p[j++]=a[i];
c++;
}
}
for(j=0;j<c;j++)
{
printf("palindrome array is =%d\n",p[j]);
}
int small=p[0];
for(j=1;j<c;j++)
{
if(small0)
{
int r=temp%10;
temp=temp/10;
sum=sum*10+r;
}
if(sum==p)
{
return 1;
}
else
{
return 0;
}
}

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