From 6379f01abc9ac35c128cb940bfe6dae046e73ea3 Mon Sep 17 00:00:00 2001
From: Linus Miller <lohfu@lohfu.io>
Date: Wed, 28 Mar 2018 13:07:45 +0200
Subject: [PATCH] Alternative solutions to problem 10

---
 0010-1.py | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 0010-2.py | 39 +++++++++++++++++++++++++++++++++++++++
 0010.py   |  2 ++
 3 files changed, 91 insertions(+)
 create mode 100644 0010-1.py
 create mode 100644 0010-2.py

diff --git a/0010-1.py b/0010-1.py
new file mode 100644
index 0000000..7897346
--- /dev/null
+++ b/0010-1.py
@@ -0,0 +1,50 @@
+from functools import reduce
+# from collections import deque
+
+n = 2000000
+# n = 100
+
+array = list(range(3, n))
+
+# array[0] = None
+# array[1] = None
+
+primes = []
+
+p = 2
+
+def next():
+    # num = array.popleft()
+
+    # while (num == None and len(array) > 0):
+    #     num = array.popleft()
+
+    # return num
+    global array
+
+    for idx, num in enumerate(array):
+        idx
+        if (num != None):
+            array = array[idx + 1:]
+
+            print(num)
+            print(idx)
+            return num
+
+while (p != None):
+    print(p)
+    primes.append(p)
+
+    count = 1
+    i = count * p - 1
+    length = len(array)
+    print(length)
+
+    for i in range(p - 1, length, p):
+        array[i] = None
+
+    p = next()
+
+
+print(primes)
+
diff --git a/0010-2.py b/0010-2.py
new file mode 100644
index 0000000..c8ee826
--- /dev/null
+++ b/0010-2.py
@@ -0,0 +1,39 @@
+# https://www.geeksforgeeks.org/sieve-sundaram-print-primes-smaller-n/
+
+from functools import reduce
+
+def sieve_of_sundaram(n):
+    # In general Sieve of Sundaram, produces primes smaller
+    # than (2*x + 2) for a number given number x.
+    # Since we want primes smaller than n, we reduce n to half
+    n_new = int((n-2) / 2);
+ 
+    # This array is used to separate numbers of the form i+j+2ij
+    # from others where  1 <= i <= j
+    marked = [ False ] * (n_new + 1)
+ 
+    # Main logic of Sundaram.  Mark all numbers of the
+    # form i + j + 2ij as true where 1 <= i <= j
+    for i in range(1, n_new + 1):
+        j = i
+
+        while (i + j + 2 * i * j < n_new):
+            marked[i + j + 2*i*j] = True
+            j += 1
+ 
+    primes = []
+
+    if (n > 2):
+        primes.append(2)
+
+    for i in range(1, n_new):
+        if (marked[i] == False):
+            primes.append(2 * i + 1)
+
+    return primes
+
+primes = sieve_of_sundaram(2000000)
+
+print(reduce(lambda x, y: x + y, primes))
+
+# answer 142913828922
diff --git a/0010.py b/0010.py
index 2006d26..8b329aa 100644
--- a/0010.py
+++ b/0010.py
@@ -12,3 +12,5 @@ for i in range(2, 2000000):
 result = reduce(lambda x, y: x + y, primes)
 print(primes)
 print(result)
+
+# answer 142913828922