【欧拉函数】 HDOJ 4483 Lattice triangle

来源：互联网发布：用软件装系统编辑：程序博客网时间：2024/05/21 00:54
看网上的题解做的。。。。
#include <iostream>  #include <queue>  #include <stack>  #include <map>  #include <set>  #include <bitset>  #include <cstdio>  #include <algorithm>  #include <cstring>  #include <climits>  #include <cstdlib>#include <cmath>#include <time.h>#define maxn 100005#define maxm 40005#define eps 1e-10//#define mod 1000000007#define INF 999999999#define lowbit(x) (x&(-x))#define mp mark_pair#define ls o<<1#define rs o<<1 | 1#define lson o<<1, L, mid  #define rson o<<1 | 1, mid+1, R  typedef long long LL;//typedef int LL;using namespace std;//LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}// headLL phi[maxn];LL a[maxn], b[maxn], c[maxn];LL n;const LL  mod = 1000000007, md = (LL) mod * 6;void init(void){phi[1] = a[1] = c[1] = 1, b[1] = 2;for(int i = 2; i < maxn; i++) if(!phi[i])for(int j = i; j < maxn; j += i) {if(!phi[j]) phi[j] = j;phi[j] -= phi[j]/i;}for(int i = 2; i < maxn; i++) {a[i] = (a[i-1] + phi[i] * 2) % mod;b[i] = (b[i-1] + phi[i] * i * 3) % mod;c[i] = (c[i-1] + phi[i] * i % mod * i % mod) % mod;}}int main(void){int _;init();while(scanf("%d", &_)!=EOF) {while(_--) {scanf("%I64d", &n), n++;LL tmp = n * n % mod, ans = 0;ans = tmp * (tmp-1) % md * (tmp-2) % md / 6;ans -= tmp * (n-1) % md * (n-2) * 2 % md / 6;tmp = 0;for(LL k = 2; k < n; k++) {LL m = (n-1)/k;tmp = (tmp + (LL)(k-1) * (a[m] % mod * n % mod * n % mod - (LL)n * k % mod * b[m] % mod + (LL)k * k % mod * c[m] % mod))%mod;}ans -= tmp*2;printf("%I64d\n", (ans % mod + mod) % mod);}}return 0;}
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