版本一：
1 #include<bits/stdc++.h> 2 #define IO ios_base::sync_with_stdio(0);cin.tie(0); 3 using namespace std; 4 int prime[32770], phi[32770]; 5 int main() 6 {IO; 7 int T; 8 cin >> T; 9 while(T --){ 10 int n; 11 cin >> n; 12 memset(prime, 1, sizeof(prime)); 13 prime[0] = 0; 14 prime[1] = 0; 15 for(int i = 2; i * i <= n; i ++){ 16 if(prime[i]){ 17 for(int j = i + i; j <= n; j += i){ 18 prime[j] = 0; 19 } 20 } 21 }//找到所有n以内的素数 22 for(int i = 1; i <= n; i ++) 23 phi[i] = i; 24 for(int i = 2; i <= n; i ++){ 25 if(prime[i]){ 26 for(int j = i; j <= n; j += i){ 27 phi[j] = phi[j] / i * (i - 1); 28 } 29 } 30 }//求出n以内所有数的欧拉值 31 cout << phi[n] << endl; 32 } 33 }
版本二：
1 #include<bits/stdc++.h> 2 #define IO ios_base::sync_with_stdio(0);cin.tie(0); 3 using namespace std; 4 int prime[32770], u[32770], phi[32770]; 5 int main() 6 {IO; 7 int T; 8 cin >> T; 9 while(T --){ 10 int n; 11 cin >> n; 12 int sum = 0; 13 phi[1] = 1; 14 memset(u, 1, sizeof(u)); 15 for(int i = 2; i <= n; i ++){ 16 if(u[i]){ 17 prime[++ sum] = i; 18 phi[i] = i - 1; 19 } 20 for(int j = 1; j <= sum; j ++){ 21 if(i * prime[j] > n) break; 22 u[i * prime[j]] = 0; 23 if(i % prime[j]){ 24 phi[i * prime[j]] = phi[i] * (prime[j] - 1); 25 } 26 else{ 27 phi[i * prime[j]] = phi[i] * prime[j]; 28 } 29 } 30 } 31 cout << phi[n] << endl; 32 } 33 }
