hdoj The Euler function 2824 （欧拉函数打表）

The Euler function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4743    Accepted Submission(s): 1983

Problem Description

The Euler function phi is an important kind of function in number theory, (n) represents the amount of the numbers which are smaller than n and coprime to n, and this function has a lot of beautiful characteristics. Here comes a very easy question: suppose you are given a, b, try to calculate (a)+ (a+1)+....+ (b)

Input

There are several test cases. Each line has two integers a, b (2<a<b<3000000).

Output

Output the result of (a)+ (a+1)+....+ (b)

Sample Input

3 100

Sample Output

3042
#include<stdio.h>#include<string.h>#include<algorithm>#define N 3000010#define ll long longusing namespace std;ll a[N];ll eular(){int i,j;memset(a,0,sizeof(a));a[1]=1;for(i=2;i<N;i++){if(!a[i]){for(j=i;j<N;j+=i){if(!a[j])a[j]=j;a[j]=a[j]/i*(i-1);}}}for(i=2;i<N;i++)a[i]+=a[i-1];}int main(){int l,r;eular();while(scanf("%d%d",&l,&r)!=EOF){printf("%I64d\n",a[r]-a[l-1]);}return 0;}