Solve problem 206

python/e206.py

@@ -0,0 +1,36 @@
+import math
+
+
+def is_square(apositiveint):
+    """ From: https://stackoverflow.com/a/2489519 """
+    x = apositiveint // 2
+    seen = set([x])
+    while x * x != apositiveint:
+         x = (x + (apositiveint // x)) // 2
+         if x in seen: return False
+         seen.add(x)
+    return True
+
+
+def canditates(current_value, depth):
+    if depth <= 0:
+        yield current_value
+    else:
+        d = 10 ** depth
+        for i in range(10):
+            for new_value in canditates(current_value - i * d, depth - 2):
+                yield new_value
+
+
+def euler_206():
+    c = 1929394959697989990
+    for i, c in enumerate(canditates(c, 17)):
+        if is_square(c):
+            return int(math.sqrt(c))
+
+
+if __name__ == "__main__":
+    solution = euler_206()
+    print("e206.py: " + str(solution))
+    assert(solution == 1389019170)
+

python/lib_create_templates.py

@@ -1,5 +1,5 @@
-FROM = 88
+FROM = 206
-TILL = 90
+TILL = 206
 
 template = """
 def euler_XXX():
@@ -14,8 +14,12 @@ if __name__ == "__main__":
 
 
 for i in range(FROM, TILL + 1):
-    e = "0" + str(i)
+    if i < 100:
+        e = "0" + str(i)
+    else:
+        e = str(i)
     filename = "e" + e + ".py"
     with open(filename, "w") as f:
         s = template.replace("XXX", e)
         f.write(s)
+