'commit'

TangDou/AcWing/RongChi/HDU2204_2.cpp

@@ -1,38 +1,40 @@
 #include <bits/stdc++.h>
 using namespace std;
-#define ll long long
+#define LL long long
 const int N = 100 + 100;
-ll mu[N * 100], primes[N * 100], st[N * 100];
-int cnt;
 
-void get_mobius() {
+LL mu[N], sum[N];
+int primes[N], cnt;
+bool st[N];
+void get_mobius(LL n) {
     mu[1] = 1;
-    for (int i = 2; i < N; i++) {
+    for (LL i = 2; i <= n; i++) {
         if (!st[i]) {
             primes[cnt++] = i;
             mu[i] = -1;
         }
-        for (int j = 0; j < cnt; j++) {
+        for (LL j = 0; primes[j] <= n / i; j++) {
-            ll t = primes[j] * i;
+            LL t = primes[j] * i;
-            if (primes[j] > N / i) {
+            st[t] = true;
-                break;
-            }
-            st[t] = 1;
             if (i % primes[j] == 0) {
                 mu[t] = 0;
                 break;
             }
-            mu[t] = -mu[i];
+            mu[t] = mu[i] * -1;
         }
     }
+    // 维护u(x)前缀和
+    for (LL i = 1; i <= n; i++) sum[i] = sum[i - 1] + mu[i];
 }
+
 int main() {
-    get_mobius();
+    get_mobius(N - 1);
-    ll tmp;
+
+    LL tmp;
     while (cin >> tmp) {
-        ll sum = 1;
+        LL sum = 1;
-        for (ll i = 2; i <= 64; i++) {
+        for (LL i = 2; i <= 64; i++) {
-            sum -= mu[i] * (ll)(pow(tmp * 1.0, 1.0 / i) - 1);
+            sum -= mu[i] * (LL)(pow(tmp * 1.0, 1.0 / i) - 1);
         }
         cout << sum << endl;
     }