some programs!

cs101/dh_20260923_04_lamps.cpp

@@ -0,0 +1,30 @@
+#include <iostream>
+
+constexpr int MAX_N = 1001;
+
+int n;
+bool lamps[MAX_N]; // 第 0 盏放弃
+
+void simulate() {
+    for (int i = 1; i <= n; i++) {
+        for (int j = 0; j <= n; j += i) {
+            lamps[j] = !lamps[j];
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+    std::cin >> n;
+    simulate();
+
+    for (int i = 1; i <= n; i++) {
+        if (!lamps[i]) {
+            std::cout << i << " ";
+        }
+    }
+    std::cout << std::endl;
+
+    return 0;
+}