Palindrome:
If a number reads the same both forward and backward, it is called a Palindrome number. And the insane part is that it doesn’t just apply to numbers. Even if a string reads the same in both directions, it is always a Palindrome!
Examples for string palindrome
Example 1:
Input:
given_string = madam
Output:
The given string madam is palindrome
Explanation:
Here the madam word reads same from front and end so it is palindrome
Example 2:
Input:
given_string = vicky
Output:
The given string vicky is not palindrome
Explanation:
Here vicky and ykciv are not equal so it is not a palindrome
Examples for number palindrome
Example 1:
Input:
given_number =12321
Output:
The given number 12321 is palindrome
Explanation:
Here the number 12321 reads same from front and end so it is palindrome
Example 2:
Input:
given_number =12345
Output:
The given number 12345 is not palindrome
Explanation:
Here 12345 and 54321 are not equal so it is not a palindrome
Checking Palindrome in Python
There are several ways to check whether the given number is palindrome or not some of them are:
- Using while loop to check whether the number is palindrome
- Using for loop and string concatenation to check whether the number is palindrome
- Using for loop and string concatenation to check whether the string is palindrome
- Using slicing to check whether the number is palindrome
- Using slicing to check whether the string is palindrome
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Method #1:Using while loop to check whether the number is palindrome
Algorithm:
- Scan the given number
- Take another variable say duplicate_num and initialize it with given number
- Set the variable reverse_number to 0.
- Loop while number > 0 Loop while number > 0
- Multiply reverse_number by 10 and add the remainder to reverse_number like below
- reverse_number = (reverse_number * 10) + remainder
- Divide the given number by 10 to remove the last digit.
- If the duplicate_num and reverse_number are equal then it is palindrome.
- Else it is not palindrome.
Below is the implementation:
# given number
given_num = 12321
# taking another variable to store the copy of original number
# and initialize it with given num
duplicate_num = given_num
# Take a variable reverse_number and initialize it to null
reverse_number = 0
# using while loop to reverse the given number
while (given_num > 0):
# implementing the algorithm
# getting the last digit
remainder = given_num % 10
reverse_number = (reverse_number * 10) + remainder
given_num = given_num // 10
# if duplicate_num and reverse_number are equal then it is palindrome
if(duplicate_num == reverse_number):
print("The given number", duplicate_num, "is palindrome")
else:
print("The given number", duplicate_num, "is not palindrome")
Output:
The given number 12321 is palindrome
Method #2: Using for loop and string concatenation to check whether the number is palindrome
Approach:
- Scan the given number.
- Take a empty string say revstring.
- Convert the given number to string using str() function say strnum for this string.
- Traverse every character of the string using for loop in reverse order using range function.
- Add each character to revstring using string concatenation.
- If the revstring and string_num are equal then it is palindrome.
- Else it is not palindrome.
Below is the Implementation:
# given number
given_num = 12321
# taking empty string
reverse_string = ""
# Convert the given_num to string using str
strnum = str(given_num)
# calculating the length of string
length = len(strnum)
# Traverse the strnum string in reverse order using for loop range function
for index in range(length-1, -1, -1):
# add the character to reverse_string using string concatenation
reverse_string = reverse_string+strnum[index]
# if reverse_string and strnum are equal then it is palindrome
if(reverse_string == strnum):
print("The given number", given_num, "is palindrome")
else:
print("The given number", given_num, "is not palindrome")
Output:
The given number 12321 is palindrome
Method #3:Using for loop and string concatenation to check whether the string is palindrome
Approach:
- Scan the givenstring.
- Take a empty string say revstring.
- Traverse every character of the string using for loop in reverse order using range function.
- Add each character to revstring using string concatenation.
- If the revstring and givenstring are equal then it is palindrome.
- Else it is not palindrome.
Below is the Implementation:
# given string
given_string = "madam"
# taking empty string
reverse_string = ""
# calculating the length of string
length = len(given_string)
# Traverse the strnum string in reverse order using for loop range function
for index in range(length-1, -1, -1):
# add the character to reverse_string using string concatenation
reverse_string = reverse_string+given_string[index]
# if reverse_string and strnum are equal then it is palindrome
if(reverse_string == given_string):
print("The given string", given_string, "is palindrome")
else:
print("The given string", given_string, "is not palindrome")
Output:
The given string madam is palindrome
Method #4:Using slicing to check whether the number is palindrome
Approach:
- Scan the given number.
- Convert the given number to string using str() function say strnum for this string.
- Reverse the string using slicing
- If the revstring and string_num are equal then it is palindrome.
- Else it is not palindrome.
Below is the implementation:
# given number
given_num = 12321
# Convert the given_num to string using str
strnum = str(given_num)
# calculating the length of string
length = len(strnum)
# Reversing the string using slicing
reverse_string = strnum[len(strnum)::-1]
# if reverse_string and strnum are equal then it is palindrome
if(reverse_string == strnum):
print("The given number", given_num, "is palindrome")
else:
print("The given number", given_num, "is not palindrome")
Output:
The given number 12321 is palindrome
Method #5: Using slicing to check whether the string is palindrome
Approach:
- Scan the given string.
- Reverse the string using slicing
- If the revstring and string are equal then it is palindrome.
- Else it is not palindrome.
Below is the implementation:
# given string
given_string = "madam"
# calculating the length of string
length = len(given_string)
# Reversing the string using slicing
reverse_string = given_string[len(given_string)::-1]
# if reverse_string and strnum are equal then it is palindrome
if(reverse_string == given_string):
print("The given string", given_string, "is palindrome")
else:
print("The given string", given_string, "is not palindrome")
Output:
The given string madam is palindrome
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