light oj 1007 - Mathematically Hard
Mathematically some problems look hard. But with the help of the computer, some problems can be easily solvable.
In this problem, you will be given two integers a and b. You have to find the summation of the scores of the numbers from a to b (inclusive). The score of a number is defined as the following function.
score (x) = n2, where n is the number of relatively prime numbers with x, which are smaller than x
For example,
For 6, the relatively prime numbers with 6 are 1 and 5. So, score (6) = 22 = 4.
For 8, the relatively prime numbers with 8 are 1, 3, 5 and 7. So, score (8) = 42 = 16.
Now you have to solve this task.
Input
Input starts with an integer T (≤ 105), denoting the number of test cases.
Each case will contain two integers a and b (2 ≤ a ≤ b ≤ 5 * 106).
Output
For each case, print the case number and the summation of all the scores from a to b.
Sample Input |
Output for Sample Input |
3 6 6 8 8 2 20 |
Case 1: 4 Case 2: 16 Case 3: 1237 |
Note
Euler‘s totient function applied to a positive integer n is defined to be the number of positive integers less than or equal to n that are relatively prime to n. is read "phi of n."
Given the general prime factorization of , one can compute using the formula
題目大意:求出a到b之間所有數本身與小於其本身互素的數的個數的平方和(歐拉函數打表,區間平方和打表)。
題不是很難卡在了數據類型上,錯了好幾次(反思)。需要用到unsigned long long
#include<stdio.h> #include<string.h> #include<math.h> #include<algorithm> #define LL unsigned long long using namespace std; int phi[5000005]={0}; LL sum[5000005]={0}; void inin1() { for(int i=2; i<5000002; i++) { if(phi[i]==0) for(int j=i; j<=5000002; j+=i) { if(phi[j]==0)phi[j]=j; phi[j]=phi[j]/i*(i-1); } } } void inin2() { for(int i=2; i<=5000000; i++) sum[i]=sum[i-1]+(LL)phi[i]*(LL)phi[i]; } int main() { inin1(); inin2(); int T, t=1; scanf("%d", &T); while(T--) { int a, b; scanf("%d%d", &a, &b); printf("Case %d: %llu\n", t++, sum[b]-sum[a-1]); } return 0; }View Code
light oj 1007 - Mathematically Hard