Linear sieve && Euler functions for prime numbers

O (n) Filter primes

#include <bits/stdc++.h>using namespace Std;const int M = 1e6 + ten; int mindiv[m];//min factorization int prim[m], pnum;//per number prime bool vis[m]; void Prim () {for        (int i = 2; i < M; i + +) {                if (!vis[i]) {                        mindiv[i] = i;                        prim[pnum++] = i;                }                for (int j = 0; J < Pnum; J + +) {                        if (I*prim[j] >= M) break;                        vis[I*prim[j]] = 1;                        Mindiv[i] = prim[j];                        if (i% prim[j] = = 0) break;}}}        int main () {        prim ();        return 0;}

Euler function O (n): Phi[i] is the number of the number of I coprime within the range of <= I

#include <bits/stdc++.h>using namespace Std;const int M = 1e6 + ten; int mindiv[m]; int prim[m], pnum; bool Vis[m]; I NT Phi[m]; Euler function int Euler () {        phi[1] = 1;        for (int i = 2; i < M; i + +) {                if (Vis[i] && phi[i] = = 0) {Phi[i] = pnum;}                if (!vis[i]) {                        prim[pnum++] = i;                        Phi[i] = i-1;                        MinDiv [i] = i;                }                for (int j = 0; J < Pnum; J + +) {                        if (i * prim[j] >= M) break;                        vis[I*prim[j]] = 1;                        MinDiv [i*prim[j]] = prim[j];                        if (i% prim[j] = = 0) break;                        else phi[i*prim[j]] = phi[i] * phi[prim[j];}                }        } int main () {        Euler ();        return 0;}

　　

Linear sieve && Euler functions for prime numbers