Solves Problem 55

README.markdown

@@ -66,13 +66,13 @@ So you may find some of the code here quite ugly. And this is the case :). Why o
 50 - Which prime, below one-million, can be written as the sum of the most consecutive primes? - **~= 1 hour** <br />
 52 - Find the smallest positive integer, x, such that 2x, 3x, 4x, 5x, and 6x, contain the same digits. - 2min <br />
 53 - How many values of C(n,r), for 1 <= n <= 100, exceed one-million? - < 1 sec <br />
+55 - How many Lychrel numbers are there below ten-thousand? - < 1 sec <br />
 56 - Considering natural numbers of the form, a^b, finding the maximum digital sum. > 3 sec <br />
 67 - Using an efficient algorithm find the maximal sum in the triangle? - 0.027 <br />
 
 ## In progress:
 
 47 - Find the first four consecutive integers to have four distinct primes factors. <br />
-55 - How many Lychrel numbers are there below ten-thousand? <br />
 97 - Find the last ten digits of the non-Mersenne prime: 28433 <20> 2^7830457 + 1. <br />
 
 ## Contact

e_55.py

@@ -41,10 +41,17 @@ the theoretical nature of Lychrel numbers.
  ##---
  """
 
+def is_palindromic(num):
+    """
+    Returns True if num is palindromic
+    Ex : 121
+    """
+    return (num == reverse(num))
 
 def reverse(num):
     """
-    Returns the palidromic number of num
+    Returns the reverse number of num
+    ex : 123 returns 321
     """
     str_num = str(num)
     rev = ''
@@ -54,6 +61,22 @@ def reverse(num):
     return int(rev)
 
 
+def is_lychrel(num, max_it=50):
+    """
+    Given a maximu number of iterations,
+    returns True if num is a lychrel number
+    """
+    cur = num
+    it = 1
+    while it < max_it:
+        cur = cur + reverse(cur)
+        if is_palindromic(cur):
+            return False
+        it += 1
+
+    return True
+
+
 def count_lychrel(max_num, max_it=50):
     """
     Returns the number of lychrel numbers smaller than max_num
@@ -62,11 +85,12 @@ def count_lychrel(max_num, max_it=50):
     """
     lychrels = []
     for i in xrange(1, max_num + 1):
-        cur = i
+        if (is_lychrel(i, max_it)):
+            lychrels.append(i)
 
-    return 1
+    print lychrels
+    return len(lychrels)
 
 
 if __name__ == '__main__':
-    print palindrome(12345)
-    #print "Answer : %d " % (count_lychrel(10000))
+    print "Answer : %d " % (count_lychrel(10000))