atcoder/abc052C

Author: xirc

atcoder/abc052/C/main.cpp

@@ -0,0 +1,57 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+ll const MOD = 1e9+7;
+int const M = 1e3+1;
+
+set<int> seive() {
+    vector<bool> is_prime(M, true);
+    is_prime[0] = is_prime[1] = false;
+    for (int i = 2; i * i <= M; ++i) {
+        if (!is_prime[i]) continue;
+        for (int j = i * 2; j < M; j += i) {
+            is_prime[j] = false;
+        }
+    }
+
+    set<int> primes;
+    for (int i = 2; i < M; ++i) {
+        if (is_prime[i]) {
+            primes.insert(i);
+        }
+    }
+    return primes;
+}
+
+ll solve(int N) {
+    auto primes = seive();
+    vector<int> factors(M, 0);
+    for (int i = N; i >= 2; --i) {
+        int v = i;
+        for (auto p : primes) {
+            while (v % p == 0) {
+                v /= p;
+                ++factors[p];
+            }
+        }
+    }
+
+    ll ans = 1;
+    for (int i = 0; i < M; ++i) {
+        ans = (ans * (factors[i]+1)) % MOD;
+    }
+    return ans;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    int N;
+    cin >> N;
+    cout << solve(N) << endl;
+
+    return 0;
+}