P4397 [JLOI2014]聪明的燕姿

https://www.luogu.com.cn/record/88041741

Luogu/P4397/P4397.cpp

@@ -0,0 +1,79 @@
+#include <iostream>
+#include <algorithm>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int cnt;
+long long s, ans[500005];
+int p, primes[50005];
+bool not_prime[50005];
+
+bool is_prime(long long x) {
+    if (x < 2) return false;
+
+    for (int i = 2; static_cast<long long>(i) * i <= x; i++) {
+        if (x % i == 0) return false;
+    }
+
+    return true;
+}
+
+void dfs(long long now, int pos, long long sum) {
+    if (now == 1) {
+        ans[++cnt] = sum;
+
+        return;
+    }
+
+    if (is_prime(now - 1) && now > primes[pos]) {
+        ans[++cnt] = (now - 1) * sum;
+    }
+
+    for (int i = pos;
+         static_cast<long long>(primes[i]) * primes[i] <= now;
+         i++) {
+        for (long long t = primes[i],
+                       s = t + 1;
+             s <= now;
+             s += t *= primes[i]) {
+            if (now % s == 0) {
+                dfs(now / s, i + 1, sum * t);
+            }
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    for (int i = 2; i <= 50000; i++) {
+        if (!not_prime[i]) primes[++p] = i;
+
+        for (int j = 1; i * primes[j] <= 50000; j++) {
+            not_prime[i * primes[j]] = true;
+            if (i % primes[j] == 0) break;
+        }
+    }
+
+    while (cin >> s) {
+        cnt = 0;
+
+        dfs(s, 1, 1);
+        std::sort(ans + 1, ans + cnt + 1);
+
+        cout << cnt << endl;
+
+        if (cnt) {
+            for (int i = 1; i <= cnt; i++) {
+                cout << ans[i] << ' ';
+            }
+
+            cout << endl;
+        }
+    }
+
+    return 0;
+}