添加 'E.cpp'

E.cpp

@@ -0,0 +1,51 @@
+#include <bits/stdc++.h>
+ 
+using namespace std;
+vector<int> phi;
+ 
+void genPhi(int max) {
+    int minDiv[max];
+    for (int i = 1; i < max; i++) {
+        minDiv[i] = i;
+    }
+    for (int i = 2; i * i < max; i++) {
+        if (minDiv[i] == i) {
+            for (int j = i * i; j < max; j += i) {
+                minDiv[j] = i;
+            }
+        }
+    }
+    phi[1] = 1;
+    for (int i = 2; i < max; i++) {
+        phi[i] = phi[i / minDiv[i]];
+        if ((i / minDiv[i]) % minDiv[i] == 0) {
+            phi[i] *= minDiv[i];
+        } else {
+            phi[i] *= minDiv[i] - 1;
+        }
+    }
+}
+ 
+const int MAXN = 1000001;
+long long g[MAXN];
+int f[MAXN];
+ 
+int main() {
+//    ofstream cout("output.txt");
+    phi.resize(MAXN);
+    genPhi(MAXN);
+    for (int i = 1; i <= MAXN; i += 2) {
+        f[i] = phi[i] % (i + 1);
+    }
+    g[0] = 0;
+    for (int i = 1; i <= MAXN; i++) {
+        g[i] = g[i - 1] + f[i];
+    }
+    int T;
+    cin >> T;
+    for (int t = 1; t <= T; t++) {
+        int n;
+        cin >> n;
+        cout << "Case " << t << ": " << g[n] << endl;
+    }
+}