'commit'

TangDou/AcWing_TiGao/T5/FenJieZhiYinShu/197.cpp

@@ -0,0 +1,35 @@
+#include <bits/stdc++.h>
+using namespace std;
+typedef long long LL;
+
+// 欧拉筛
+const int N = 1e6 + 10;
+int primes[N], cnt; // primes[]存储所有素数
+bool st[N];         // st[x]存储x是否被筛掉
+void get_primes(int n) {
+    memset(st, 0, sizeof st);
+    cnt = 0;
+    for (int i = 2; i <= n; i++) {
+        if (!st[i]) primes[cnt++] = i;
+        for (int j = 0; primes[j] * i <= n; j++) {
+            st[primes[j] * i] = true;
+            if (i % primes[j] == 0) break;
+        }
+    }
+}
+int main() {
+    int n;
+    cin >> n;
+
+    get_primes(n);
+
+    for (int i = 0; i < cnt; i++) {
+        int p = primes[i];
+        int s = 0;
+        // 思路：由大到小+除法降维
+        // 优点：不用考虑乘法而导致的爆int上限
+        for (int j = n; j; j /= p) s += j / p;
+        printf("%d %d\n", p, s);
+    }
+    return 0;
+}