Added optimiztions to segmented sieve

Author: fredbr

data_structures/li_chao.cpp

@@ -6,7 +6,6 @@ using ll = long long;
 
 int const maxn = 101010;
 ll const maxm = 1e9;
-ll const inf = 0x3f3f3f3f3f3f3f3f;
 
 struct Fc {
     ll a, b;
@@ -48,7 +47,7 @@ ll get(Node *t, ll l, ll r, ll x) {
         return min(t->fn.eval(x), get(t->l, l, m, x));
     else if (x > m and t->r)
         return min(t->fn.eval(x), get(t->r, m+1, r, x));
-    
+
     return t->fn.eval(x);
 }
 
@@ -62,7 +61,7 @@ int main()
     cin >> n;
 
     for (int i = 1; i <= n; i++) cin >> a[i];
-    for (int i = 1; i <= n; i++) cin >> b[i], dp[i] = inf;
+    for (int i = 1; i <= n; i++) cin >> b[i];
 
     Node *root = new Node{{b[1], 0}};
     dp[1] = b[1];

math/segmented_sieve.cpp

@@ -1,5 +1,7 @@
 #include <bits/stdc++.h>
 
+#pragma GCC optimize("O3","unroll-loops")
+
 using namespace std;
 
 uint32_t const sieve_size = 1<<17;

math/segmented_sieve_bit.cpp

@@ -0,0 +1,84 @@
+#include <bits/stdc++.h>
+
+#pragma GCC optimize("O3","unroll-loops")
+
+using namespace std;
+
+uint32_t const sieve_size = 1<<20;
+
+vector<uint64_t> solve(uint64_t l, uint64_t r) {
+	static const int64_t unset_bit[16] = {
+	  ~(1 << 0), ~(1 << 0),
+	  ~(1 << 1), ~(1 << 1),
+	  ~(1 << 2), ~(1 << 2),
+	  ~(1 << 3), ~(1 << 3),
+	  ~(1 << 4), ~(1 << 4),
+	  ~(1 << 5), ~(1 << 5),
+	  ~(1 << 6), ~(1 << 6),
+	  ~(1 << 7), ~(1 << 7)
+	};
+
+	uint64_t i = 3, s = 3, n = std::max(l|1, 3ul);
+	uint64_t sqt = std::sqrt(r);
+
+	vector<char> sieve(sieve_size), is_prime(sqt+1, true);
+	vector<uint64_t> primes, mult;
+
+	vector<uint64_t> result;
+
+	if (l <= 2 and r > 2) result.push_back(2);
+
+	for (; i*i < l; i += 2)
+		if (is_prime[i])
+			for (uint64_t j = i*i; j < sqt; j += 2*i)
+				is_prime[j] = false;
+
+	for (; s*s < l; s += 2) {
+		if (is_prime[s]) {
+			primes.push_back(s);
+			uint64_t nxt = ((l-1)/s+1)*s;
+			if (nxt == s) nxt += s;
+			if (nxt%2 == 0) nxt += s;
+			mult.push_back(nxt-l);
+		}
+	}
+
+	for (uint64_t low = l; low < r; low += sieve_size) {
+		fill(sieve.begin(), sieve.end(), 0xff);
+		uint64_t high = min(r, low+sieve_size);
+
+		for (; i*i < high; i += 2)
+			if (is_prime[i])
+				for (uint64_t j = i*i; j < sqt; j += 2*i)
+					is_prime[j] = false;
+
+		for (; s*s < high; s += 2) {
+			if (is_prime[s]) {
+				primes.push_back(s);
+				mult.push_back(s*s - low);
+			}
+		}
+
+		for (size_t j = 0; j < primes.size(); j++) {
+			uint64_t k = mult[j];
+			for (uint64_t prime = primes[j]*2; k < sieve_size; k += prime)
+				sieve[k>>4] &= unset_bit[k&15];
+			mult[j] = k-sieve_size;
+		}
+
+		for (; n < high; n += 2)
+			if (sieve[(n-low)>>4]&~unset_bit[(n-low)&15])
+				result.push_back(n);
+	}
+
+	return result;
+}
+
+int main() {
+	uint64_t l, r;
+	cin >> l >> r;
+
+	auto ans = solve(l, r+1);
+
+	for (auto p : ans) cout << p << "\n";
+}