HDU

HDU - 2824

题意：

　　求【a，b】间的欧拉函数和。这道题卡内存，只能开一个数组。

思路：

　　ϕ(n) = n * （p-1)/p * ... 可利用线性筛法求出所有ϕ(n) 。

　　

#include <algorithm>
#include  <iterator>
#include  <iostream>
#include   <cstring>
#include   <iomanip>
#include   <cstdlib>
#include    <cstdio>
#include    <string>
#include    <vector>
#include    <bitset>
#include    <cctype>
#include     <queue>
#include     <cmath>
#include      <list>
#include       <map>
#include       <set>
using namespace std;
//#pragma GCC optimize(3)
//#pragma comment(linker, "/STACK:102400000,102400000")  //c++
#define lson (l , mid , rt << 1)
#define rson (mid + 1 , r , rt << 1 | 1)
#define debug(x) cerr << #x << " = " << x << "
";
#define pb push_back
#define pq priority_queue



typedef long long ll;
typedef unsigned long long ull;

typedef pair<ll ,ll > pll;
typedef pair<int ,int > pii;
typedef pair<int ,pii> p3;
//priority_queue<int> q;//这是一个大根堆q
//priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q
#define fi first
#define se second
//#define endl '
'

#define OKC ios::sync_with_stdio(false);cin.tie(0)
#define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行
#define REP(i , j , k)  for(int i = j ; i <  k ; ++i)
//priority_queue<int ,vector<int>, greater<int> >que;

const ll mos = 0x7FFFFFFFLL;  //2147483647
const ll nmos = 0x80000000LL;  //-2147483648
const int inf = 0x3f3f3f3f;
const ll inff = 0x3f3f3f3f3f3f3f3fLL; //18
const double PI=acos(-1.0);

template<typename T>
inline T read(T&x){
    x=0;int f=0;char ch=getchar();
    while (ch<'0'||ch>'9') f|=(ch=='-'),ch=getchar();
    while (ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
    return x=f?-x:x;
}
// #define _DEBUG;         //*//
#ifdef _DEBUG
freopen("input", "r", stdin);
// freopen("output.txt", "w", stdout);
#endif
/*-----------------------show time----------------------*/
            const int maxn = 3000009;
            
            
            ll sum[maxn];
            /*
                 const int maxn = 3000009;
                int prime[316819];
                int phi[maxn];
                ll sum[maxn];
                bool flag[maxn];
                void getphi(){
                    phi[1] = 1,sum[1] = 1; 
                    int tot = 0;
                    for(int i=2; i<maxn; i++){
                        if(flag[i] == 0){
                            prime[++tot] = i;
                            phi[i] = i-1;
                        }
                        for(int j=1; i * prime[j] < maxn && j<=tot; j++){
                            flag[i*prime[j]] = 1;
                            if(i%prime[j] == 0){
                                phi[i * prime[j]] = phi[i] * prime[j];
                                break; 
                            }
                            else phi[i * prime[j]] = phi[i]*(prime[j] - 1);
                        }
                        sum[i] = sum[i-1] + phi[i];
                    }
                
                 }
            */
            void getphi(){
                    sum[1] = 1;
                    for(int i=2; i<maxn; i++){
                        if(!sum[i]){
                            for(int j=i; j<maxn; j+=i){
                                if(!sum[j])sum[j] = j;
                                sum[j] = sum[j] / i * (i-1);
                            }
                        }
                    }    
                    for(int i=1; i<maxn; i++)sum[i] += sum[i-1];        
            }
int main(){ 
            int a,b;
            getphi();
            while(~scanf("%d%d", &a, &b)){
                printf("%lld
", sum[b] - sum[a-1]);
            }

            return 0;
}

还有POJ的2478也是区间累计欧拉函数的和

#include <algorithm>
#include  <iterator>
#include  <iostream>
#include   <cstring>
#include   <iomanip>
#include   <cstdlib>
#include    <cstdio>
#include    <string>
#include    <vector>
#include    <bitset>
#include    <cctype>
#include     <queue>
#include     <cmath>
#include      <list>
#include       <map>
#include       <set>
using namespace std;
//#pragma GCC optimize(3)
//#pragma comment(linker, "/STACK:102400000,102400000")  //c++
#define lson (l , mid , rt << 1)
#define rson (mid + 1 , r , rt << 1 | 1)
#define debug(x) cerr << #x << " = " << x << "
";
#define pb push_back
#define pq priority_queue



typedef long long ll;
typedef unsigned long long ull;

typedef pair<ll ,ll > pll;
typedef pair<int ,int > pii;
typedef pair<int ,pii> p3;
//priority_queue<int> q;//这是一个大根堆q
//priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q
#define fi first
#define se second
//#define endl '
'

#define OKC ios::sync_with_stdio(false);cin.tie(0)
#define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行
#define REP(i , j , k)  for(int i = j ; i <  k ; ++i)
//priority_queue<int ,vector<int>, greater<int> >que;

const ll mos = 0x7FFFFFFFLL;  //2147483647
const ll nmos = 0x80000000LL;  //-2147483648
const int inf = 0x3f3f3f3f;
const ll inff = 0x3f3f3f3f3f3f3f3fLL; //18
const double PI=acos(-1.0);

template<typename T>
inline T read(T&x){
    x=0;int f=0;char ch=getchar();
    while (ch<'0'||ch>'9') f|=(ch=='-'),ch=getchar();
    while (ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
    return x=f?-x:x;
}
// #define _DEBUG;         //*//
#ifdef _DEBUG
freopen("input", "r", stdin);
// freopen("output.txt", "w", stdout);
#endif
/*-----------------------show time----------------------*/
            const int maxn = 1000009;
            
            
            ll sum[maxn];
            void getphi(){
                    sum[1] = 0;
                    for(int i=2; i<maxn; i++){
                        if(!sum[i]){
                            for(int j=i; j<maxn; j+=i){
                                if(!sum[j])sum[j] = j;
                                sum[j] = sum[j] / i * (i-1);
                            }
                        }
                    }    
                    for(int i=1; i<maxn; i++)sum[i] += sum[i-1];        
            }
int main(){ 
            int a;
            getphi();
            while(~scanf("%d", &a) && a){
                printf("%lld
", sum[a]);
            }

            return 0;
}