初等數論入門（搬運）

#define maxp 65536
#define ll long long

int primes[maxp];
bool notprime[maxp];                                                        // 1
 
void Eratosthenes() {
    notprime[1] = true;                                                    
    primes[0] = 0;
    for (int i = 2; i < maxp; i++) {
        if (!notprime[i]) {
            primes[++primes[0]] = i;                                       // 2 
            
            for (ll j = (ll)i*i; j < maxp; j += i) {
                notprime[j] = true;                                        // 3
            }
        }
    }
}

struct factor {
    int prime, count;
    factor() {}
    factor(int p, int c) : prime(p), count(c) {}
};

void Factorization(int n, vector <factor>& ans) {
    ans.clear();
    if (n == 1) {
        return;
    }
    for (int i = 1; i <= primes[0]; i++) {
        if (0 == n % primes[i]) {
            factor f(primes[i], 0);
            while (0 == n % primes[i]) {
                n /= primes[i];
                f.count++;
            }
            ans.push_back(f);
        }
        if (n == 1) {
            return;
        }
    }
    ans.push_back(factor(n, 1));
}

const int MAX_NUMBER = 10000010;
const int MAXP = 3163;                // (int)(sqrt(MAX_NUMBER*1.0) + 1);
#define LL long long

bool notprime[MAX_NUMBER];
int primes[MAXP];
int eula[MAX_NUMBER];

void eulaFilter() {
    int i, j;
    notprime[1] = 1;
    eula[1] = 1;

    // 1.枚举每个数
    for (i = 2; i < MAX_NUMBER; ++i) {
        if (!notprime[i]) {
            // 2.素数i的欧拉函数i-1
            eula[i] = i - 1;
            if (i < MAXP) {
                primes[++primes[0]] = i;
            }
            for (j = i + i; j < MAX_NUMBER; j += i) {
                notprime[j] = 1;
                // 3.非素数的欧拉函数为本身*素数分量(1-1/i)的乘积
                if (!eula[j]) eula[j] = j;
                eula[j] = eula[j] / i*(i - 1);
            }
        }
    }
}

标签：eula,notprime,int,MAX,入門,搬運,NUMBER,primes,數論
来源： https://www.cnblogs.com/sixiaoxiaoya/p/16339412.html