highest palindrome with 3 digit numbers in python

Question

In problem 4 from http://projecteuler.net/ it says:

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-d

Answer 1

580085 = 995 X 583, where 906609 = 993 X 913. Found it only by applying brute-forcing from top to bottom!

Answer 2

Simple:

def is_pallindrome(n):
    s = str(n)
    for n in xrange(1, len(s)/2 + 1):
        if s[n-1] != s[-n]:
            return False    
    return True

largest = 0
for j in xrange(100, 1000):
    for k in xrange(j, 1000):
        if is_pallindrome(j*k):
            if (j*k) > largest: largest = j*k
print largest

Answer 3

Here is my Python code:

max_pal = 0
for i in range(100,999):
    for j in range(100,999):
      mult = i * j 
      if str(mult) == str(mult)[::-1]: #Check if the number is palindrome
          if mult > max_pal: 
              max_pal = mult
print (max_pal)

Answer 4

ReThink: efficiency and performance

def palindrome(n):    

    maxNumberWithNDigits = int('9' * n) #find the max number with n digits

    product = maxNumberWithNDigits * maxNumberWithNDigits 

    #Since we are looking the max, stop on the first match

    while True:        
        if str(product) == str(product)[::-1]: break;

        product-=1

    return product

start=time.time()
palindrome(3)
end=time.time()-start

palindrome...: 997799, 0.000138998031616 secs

Answer 5

Here I added two 'break' to improve the speed of this program.

def is_palindrome(num):
    return str(num) == str(num)[::-1]
def max_palindrome(n):
    max_palindrome = 1
    for i in range(10**n-1,10**(n-1)-1,-1):
        for j in range(10**n-1,i-1,-1):
            if is_palindrome(i*j) and i*j > max_palindrome:
                max_palindrome = i * j
                break
            elif i*j < max_palindrome:
                break
    return max_palindrome
n=int(raw_input())
print max_palindrome(n)

Answer 6

Here is my code to solve this problem.

lst = []
for i in range(100,1000): 
    for n in range(2,i) : 
        lst.append (i* n) 
        lst.append(i*i)

lst2=[]
for i in lst: 
    if str(i) == str(i)[::-1]:
        lst2.append(i)
print max(lst2)