Segmented Sieve CPP

Author: tpriyanshu90

Math/Sieve of Eratosthenes/C++/SegmentedSieve.cpp

@@ -0,0 +1,57 @@
+//Segemented Sieve: Generate prime numbers less than N
+#include <bits/stdc++.h>
+using namespace std;
+typedef long long ll;
+void simpleSieve(ll limit, vector<ll>& prime){
+    bool isPrime[limit+1];
+    memset(isPrime, true, sizeof(isPrime));
+    for(int i=2;i*i<limit;++i){
+        if(isPrime[i]){
+            for(int j=i*i;j<limit;j+=i){
+                isPrime[j] = false;
+            }
+        }
+    }
+    for(int i=2;i<limit;i++){
+        if(isPrime[i]){
+            cout<<i<<" ";
+            prime.push_back(i);
+        }
+    }
+}
+void segmentedSieve(ll n){
+    ll limit = sqrt(n)+1;
+    vector<ll> prime;
+    simpleSieve(limit,prime);
+    ll low = limit;
+    ll high = 2*limit;
+    while(low<n){
+        if(high>n){
+            high = n;
+        }
+        bool mark[limit+1]; 
+        memset(mark, true, sizeof(mark)); 
+        for(int i=0;i<prime.size();++i){
+            ll curPrime = prime[i];
+            ll base = (low/curPrime)*curPrime;
+            if(base<low){
+                base = base + curPrime;
+            }
+            for(int j=base;j<high;j+=curPrime){
+                mark[j-low] = false;
+            }
+            if(base==curPrime)
+                mark[base-low] = true;
+        }
+        for(int i=low;i<high;i++){
+            if(mark[i-low])
+                cout<<i<<" ";
+        }
+        low = low + limit;
+        high = high + limit;
+    }
+}
+int main()
+{
+    segmentedSieve(10000);
+}