Bzoj-2190 仪仗队 欧拉函数
题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=2190
简单的欧拉函数题，实际上就是求gcd(x,y)=1, 0<=x,y<=n的对数。。
1 //STATUS:C++_AC_24MS_1584KB 2 #include <functional> 3 #include <algorithm> 4 #include <iostream> 5 //#include <ext/rope> 6 #include <fstream> 7 #include <sstream> 8 #include <iomanip> 9 #include <numeric> 10 #include <cstring> 11 #include <cassert> 12 #include <cstdio> 13 #include <string> 14 #include <vector> 15 #include <bitset> 16 #include <queue> 17 #include <stack> 18 #include <cmath> 19 #include <ctime> 20 #include <list> 21 #include <set> 22 #include <map> 23 using namespace std; 24 //#pragma comment(linker,"/STACK:102400000,102400000") 25 //using namespace __gnu_cxx; 26 //define 27 #define pii pair<int,int> 28 #define mem(a,b) memset(a,b,sizeof(a)) 29 #define lson l,mid,rt<<1 30 #define rson mid+1,r,rt<<1|1 31 #define PI acos(-1.0) 32 //typedef 33 typedef long long LL; 34 typedef unsigned long long ULL; 35 //const 36 const int N=40010; 37 const int INF=0x3f3f3f3f; 38 const int MOD=100000,STA=8000010; 39 const LL LNF=1LL<<60; 40 const double EPS=1e-8; 41 const double OO=1e15; 42 const int dx[4]={-1,0,1,0}; 43 const int dy[4]={0,1,0,-1}; 44 const int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31}; 45 //Daily Use ... 46 inline int sign(double x){return (x>EPS)-(x<-EPS);} 47 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;} 48 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;} 49 template<class T> inline T lcm(T a,T b,T d){return a/d*b;} 50 template<class T> inline T Min(T a,T b){return a<b?a:b;} 51 template<class T> inline T Max(T a,T b){return a>b?a:b;} 52 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);} 53 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);} 54 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));} 55 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));} 56 //End 57 58 int phi[N],prime[N]; 59 int cnt; 60 61 void phitable(int n) 62 { 63 int i,j; 64 cnt=0;phi[1]=1; 65 for(i=2;i<=n;i++){ 66 if(!phi[i]){ 67 prime[cnt++]=i; 68 phi[i]=i-1; 69 } 70 for(j=0;j<cnt && i*prime[j]<=n;j++){ 71 if(i%prime[j]){ 72 phi[i*prime[j]]=phi[i]*(prime[j]-1); 73 }else {phi[i*prime[j]]=phi[i]*prime[j];break;} 74 } 75 } 76 } 77 78 int n; 79 80 int main(){ 81 // freopen("in.txt","r",stdin); 82 int i,j,ans=0; 83 scanf("%d",&n); 84 phitable(n); 85 for(i=1;i<n;i++)ans+=phi[i]; 86 printf("%d\n",ans<<1|1); 87 88 return 0; 89 }
