bzoj4802: 欧拉函数

已知n，求φ(n)
Miller-Rabin + Pollard-rho 对大整数进行质因数分解，然后直接计算欧拉函数。

#include <cmath>#include <cstdio>#include <vector>#include <cstdlib>#include <iostream>#include <algorithm>using namespace std;typedef long long ll;int T, CAP = 20;ll n;inline ll inc(ll a, ll b, ll mod) {    a += b;    return a >= mod ? a - mod : a;}inline ll dec(ll a, ll b, ll mod) {    a -= b;    return a < 0 ? a + mod : a;}inline ll mul(ll a, ll b, ll mod) {    ll rst = 0;    while (b) {        if (b&1) rst = inc(rst, a, mod);        b >>= 1, a = inc(a, a, mod);    } return rst;}inline ll pow(ll a, ll b, ll mod) {    ll rst = 1;    while (b) {        if (b&1) rst = mul(rst, a, mod);        b >>= 1, a = mul(a, a, mod);    } return rst;}ll gcd(ll a, ll b) {    return a == 0 ? b : gcd(b%a, a);}inline ll range(ll l, ll r) {    return l + rand() % (r - l + 1);}inline bool witness2(ll a, ll x) {    ll m = x - 1, t = 0;    while (! (m&1)) m>>=1, ++t;    ll fac = pow(a, m, x), lst = fac;    while (t--) {        fac = mul(fac, fac, x);        if (fac == 1 and lst != 1 and lst != x - 1) return true;        lst = fac;    } return lst != 1;}inline bool MillerRabin(ll x) {    if (x < 2LL) return false;    if (x == 2LL) return true;    if (! (x&1LL)) return false;    for (int i = 1; i <= CAP; i++) {        ll a = range(2, x-1);        if (witness2(a, x)) return false;    } return true;}#define ABS(x) ((x) < 0 ? -(x) : (x))inline ll PollardRho(ll x, ll a) {    ll x1 = range(0, x - 1), x2 = x1;    while(1) {        x2 = inc(mul(x2, x2, x), a, x);        x2 = inc(mul(x2, x2, x), a, x);        ll d = gcd(ABS(x2 - x1), x);        if (d != 1 and d != x) return d;        x1 = inc(mul(x1, x1, x), a, x);        if (x1 == x2) return x;    } return x;}vector<ll> ls;void findFac(ll x) {    if (MillerRabin(x))        return ls.push_back(x), void(0);    ll p = x;    while (p >= x) p = PollardRho(p, range(0, x - 1));    findFac(p), findFac(x / p);}int main() {    srand(23333);    cin >> n;    if (n == 1) return puts("1"), 0;    if (MillerRabin(n)) cout << n - 1 << endl;    else {        findFac(n);        sort(ls.begin(), ls.end());        ls.erase(unique(ls.begin(), ls.end()), ls.end());        ll phi = n;        for (vector<ll>::iterator i = ls.begin(); i != ls.end(); ++i)            phi = (phi/(*i))*((*i)-1);        cout << phi << endl;    }    return 0;}