Palindrome Number

Palindrome number are very common question we face in programming field .

Palindrome number :

Numbers that remain the same when digit is reversed .

Example : 2, 202 , 101 ,191, 99599, 76567 these are palindrome number

Not palindrome : 123, 3452, 6789, 23434 4561, 34546

How check Number Is Palindrome Or Not :

There are many ways to  check number is palindrome :

Reverse Number 

  If Reversed Num == Number then it is palindrome

Example : a=2353  and reverse(a) = 3532

  Since a not equal to reverse(a) so not Palindrome

By iteration :

Compare first digit by last then second by second last until any mismatch found or we reach at mid of number . If mismatch found then it is not a palindrome number   else it is a palindrome number .

PYThon code to find palindrome number in a given range and store it to a text File :

1. # Python 2.7
2. # store Palindrome Number in given range to a text file
4. def palindrome_in_range(a,b):
5.     '''find palindrome number in range a,b and return a list of these number'''
6.     ls =[] #where all palindrome are going to store
7.     for i in range(a,b):
8.         temp = str(i)   # convert to string
9.         l = len(temp) - 1  # index of last char of string
10.         i=0 #index of first chr of string
11.        
13.         flag = True  # flag == false if number failes test of palindrome
14.         while(i<l) :
15.             ''' check for number is palindrome'''
16.             if temp[i]==temp[l] : #then check next chr
17.                 i +=1
18.                 l -=1  
19.             else:
20.                 flag = False
21.                 break
22.            
23.         if flag: #if flag == True then number is palindrome so add it to list
24.             ls.append(temp)
25.            
26.     return ls
27. def data_store(ls,a,b):
28.     '''list as input & write its content to a text file palindrome.txt '''
29.     count = 0 #use to format text in file ,ie only fixed number of number in a line
30.     f=open('palindrome.txt','w') #open text file
31.     f.write('\n\t\t\tPALINDROME number in range '+a+' to '+b)
32.     f.write('\n\t\t\t\t http://beginer2cs.blogspot.com\n\n\t\t\t')
34.     for i in ls:  #write content of ls in text file
35.         if count==10:
36.              f.write('\n\t\t\t'+str(i))
37.              count =0
38.         else:
39.             count +=1
40.             f.write(str(i)+' ,')
41.            
42.     f.close() #close file
43. if __name__=='__main__':
44.     a,b=raw_input('Enter Value of a and b separated by space :').split(' ')
45.     ls = palindrome_in_range(int(a),int(b))
47.     data_store(ls,a,b) #call func that store data in txt file
48.     print """
49.    ALL palindrome number in given range is successfully fetch
50.    and store to Palindrome.txt file .\n
51.    Thanks
52.    """

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Output of this program is stored in palindrome.txt file .which is automatically created

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Now , If we got a question to find out number of palindrome in given range (max range should be between 0 to 10000)

Yo have two ways to solve this ,

Way 1 :

Iterate through all numbers in range  and check is palindrome , if palindrome increment count by 1

Way 2:

 Use your previous learning if you have list of all palindrome number in range 0 to 100000
create a list contain all numbers , and count numbers in list which is in given range , That is our answer for above question it is very fast as compare to way 1 .

Python Program for Number of Palindrome In Given range (max range should be between 0 to 10000) : 

2. def count_palindrome(a,b):
3.     count = 0
4.     ls=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99,
5.    101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222,
6.    232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353,
7.    363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484,
8.    494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616,
9.    626, 636, 646, 656, 666, 676, 686, 696, 707, 717, 727, 737, 747,
10.    757, 767, 777, 787, 797, 808, 818, 828, 838, 848, 858, 868, 878,
11.    888, 898, 909, 919, 929, 939, 949, 959, 969, 979, 989, 999, 1001,
12.    1111, 1221, 1331, 1441, 1551, 1661, 1771, 1881, 1991, 2002, 2112,
13.    2222, 2332, 2442, 2552, 2662, 2772, 2882, 2992, 3003, 3113, 3223,
14.    3333, 3443, 3553, 3663, 3773, 3883, 3993, 4004, 4114, 4224, 4334,
15.    4444, 4554, 4664, 4774, 4884, 4994, 5005, 5115, 5225, 5335, 5445,
16.    5555, 5665, 5775, 5885, 5995, 6006, 6116, 6226, 6336, 6446, 6556,
17.    6666, 6776, 6886, 6996, 7007, 7117, 7227, 7337, 7447, 7557, 7667,
18.    7777, 7887, 7997, 8008, 8118, 8228, 8338, 8448, 8558, 8668, 8778,
19.    8888, 8998, 9009, 9119, 9229, 9339, 9449, 9559, 9669, 9779, 9889,
20.    9999]
21.     for i in ls:
22.         if i>=a and i<=b:
23.             count +=1
24.     return count
25. if __name__=='__main__':
26.     tc = int(raw_input())
27.     for i in range(tc):
28.         a,b=raw_input().split(' ')
29.         print count_palindrome(int(a),int(b))
30. 
    

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Working Range of This program can be extended by extending palindrome numbers in list

Thanks :)