hdoj 2824 The Euler function

The Euler function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4548    Accepted Submission(s): 1895

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

 

代码：

 

#include<stdio.h>#define MAX 3000010long long euler[MAX];int init(){int i,j;for(i=2;i<MAX;i++){if(!euler[i]){for(j=i;j<MAX;j+=i){if(!euler[j])euler[j]=j;euler[j]=euler[j]/i*(i-1);}}euler[i]+=euler[i-1];}}int main(){int a,b;init();while(scanf("%d%d",&a,&b)!=EOF){printf("%lld\n",euler[b]-euler[a-1]);}return 0;}