#1737. 【2022.11.7 NOIP 模拟赛】荤数（brime）

https://sjzezoj.com/submission/63729

S2OJ/1737/1737.cpp

@@ -0,0 +1,32 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e7 + 5;
+
+long long l, r, k, ans;
+int cnt, primes[N];
+bool vis[N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> l >> r >> k;
+
+    for (long long i = 2; i * i <= r && i <= k; i++) {
+        for (long long j = std::max(((l + i - 1) / i) * i, i * 2); j <= r; j += i) {
+            vis[j - l + 1] = true;
+        }
+    }
+
+    for (long long i = l; i <= r; i++) {
+        if (!vis[i - l + 1]) ans ^= i;
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}