Added a SieveOfEratosthenes class

Algorithms.hpp

@@ -28,6 +28,8 @@
 #include <algorithm>
 #include <string>
 #include <cmath>
+#include <unordered_map>
+#include <map>
 
 namespace mee{
 
@@ -93,6 +95,41 @@ T findMax(const std::vector<T>& ary);
 int findNumOccurrence(std::string str, char ch);
 
 
+template <class T>
+class SieveOfEratosthenes{
+private:
+	T possiblePrime;	//The next number that could be a prime
+	std::unordered_map<T, std::vector<T>> compositeMap;	//A map to keep track of all of the composite numbers
+public:
+	SieveOfEratosthenes(): possiblePrime(2){}
+	bool hasNext(){
+		return true;
+	}
+	T next(){
+		T prime;
+		if(possiblePrime > 2){
+			//Loop until you find a prime number
+			for(;compositeMap[possiblePrime].size() > 0;possiblePrime += 2){
+				//Create the next entry for all entries in the map
+				for(T num : compositeMap[possiblePrime]){
+					compositeMap[possiblePrime + num + num].push_back(num);
+				}
+				//Delete the current entry
+				compositeMap.erase(possiblePrime);
+			}
+			//If the number is a prime
+			//Save that it is a prime
+			prime = possiblePrime;
+			//Add the next entry to the prime
+			compositeMap[prime * 3].push_back(prime);
+			possiblePrime += 2;
+		}
+		else{
+			prime = possiblePrime++;
+		}
+		return prime;
+	}
+};
 //This is a function that returns all the primes <= goalNumber and returns a vector with those prime numbers
 template <class T>
 std::vector<T> getPrimes(T goalNumber){