hdu 2824 The Euler function(欧拉函数)
2013-08-12 18:33
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The Euler function
[b]Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 3004 Accepted Submission(s): 1230
[/b]
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
Source
2009 Multi-University Training
Contest 1 - Host by TJU
Recommend
gaojie
题意:求那个式子啊..
题解:先把欧拉函数的表用筛素数的方法搞出来
#include<stdio.h> #include<string.h> #define inf 3000000 long long f[inf+5]; void div() { int i,j; memset(f,0,sizeof(f)); f[0]=0; f[1]=1; for(i=2; i<=inf; i++) { if(!f[i]) { for(j=i; j<=inf; j+=i) { if(!f[j]) f[j]=j; f[j]=f[j]/i*(i-1); } } f[i]+=f[i-1]; } } int main() { int a,b; div(); while(scanf("%d%d",&a,&b)>0) { if(a>b) a^=b^=a^=b; printf("%I64d\n",f[b]-f[a-1]); } return 0; }
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