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 long
using 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;
}
