added module for common operations (like prime sieve)

1 files changed, 32 insertions, 0 deletions

diff --git a/src/projecteuler/common.py b/src/projecteuler/common.py
new file mode 100644
index 0000000..dafed9c
--- /dev/null
+++ b/src/projecteuler/common.py
@@ -0,0 +1,32 @@
+
+class sieve:
+	limit = 100
+
+	def __init__(self, limit):
+		self.limit = limit
+		self.number_list = [False] + [True]*(self.limit-1)
+		self.list_len = len(self.number_list)
+
+	def next_prime(self, i):
+		x = i+1
+		while(x <= self.list_len):
+			if self.number_list[x-1] == True:
+				break
+			x += 1
+		return x
+
+	def primes(self):
+		i = 2
+		while(i*i <= self.list_len):
+			x = i*i
+			while(x <= self.list_len):
+				self.number_list[x-1] = False
+				x += i
+			i = self.next_prime(i)
+
+		primeset = set()
+		for i in xrange(1, self.limit+1):
+			if self.number_list[i-1]:
+				primeset.add(i)
+		return primeset
+