# BZOJ - 2005 莫比乌斯水题

$gcd=k+1$时,每一个的贡献都是$2k+1$
$gcd=1$时,每一个贡献为$1$

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<string>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<map>
#define rep(i,j,k) for(register int i=j;i<=k;i++)
#define rrep(i,j,k) for(register int i=j;i>=k;i--)
#define iin(a) scanf("%d",&a)
#define lin(a) scanf("%lld",&a)
#define din(a) scanf("%lf",&a)
#define s0(a) scanf("%s",a)
#define s1(a) scanf("%s",a+1)
#define print(a) printf("%lld",(ll)a)
#define enter putchar('\n')
#define blank putchar(' ')
#define println(a) printf("%lld\n",(ll)a)
#define IOS ios::sync_with_stdio(0)
using namespace std;
const int maxn = 1e6+11;
const double eps = 1e-7;
typedef long long ll;
const int oo = 0x3f3f3f3f;
ll x=0,f=1;register char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
int prime[maxn],mu[maxn],tot;
bool vis[maxn],isprime[maxn];
ll sum[maxn];
void get(int n){
mu[1]=1;
rep(i,2,n){
if(!vis[i])prime[++tot]=i,mu[i]=-1;
rep(j,1,tot){
if(i*prime[j]>maxn)break;
vis[i*prime[j]]=1;
if(i%prime[j]==0){
mu[i*prime[j]]=0;
break;
}else{
mu[i*prime[j]]=-mu[i];
}
}
}
rep(i,1,n){
sum[i]=sum[i-1]+mu[i];
}
}
ll cal(int n,int m){
if(n>m) swap(n,m);
ll ans=0;int pos=0;
for(int i=1;i<=n;i=pos+1){
pos=min(n/(n/i),m/(m/i));
ans+=(sum[pos]-sum[i-1])*(n/i)*(m/i);
}
return ans;
}
int main(){
int n,m;
get(maxn-1);
while(cin>>n>>m){
int tmp=min(n,m);
ll ans=0;
rep(i,1,tmp){
if(i==1) ans+=cal(n/i,m/i);
else ans+=cal(n/i,m/i)*(2*(i-1)+1);
}
println(ans);
}
return 0;
}

posted @ 2018-03-04 16:32  Caturra  阅读(76)  评论(0编辑  收藏