poj 2649 Factovisors

　　继续做一下分解质因数的水题！

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <iostream>

#define debug 0

using namespace std;

typedef __int64 ll;
const int maxn = 100005;

bool np[maxn];
int pn, pr[maxn >> 2];

void gp(){
    memset(np, 0, sizeof(np));
    np[0] = np[1] = true;
    pn = 0;
    for (int i = 2; i < maxn; i++){
        if (!np[i]) pr[pn++] = i;
        for (int j = 0; j < pn && pr[j] * i < maxn; j++){
            np[pr[j] * i] = true;
            if (i % pr[j] == 0) break;
        }
    }
    #if debug
    printf("pn %d\n", pn);
    #endif
}

void fac(int a, int *f, int *n, int &cnt){
    int i = 0;

    cnt = 0;
    if (!a) return ;
    while (pr[i] * pr[i] <= a && i < pn){
        if (a % pr[i] == 0){
            f[cnt] = pr[i];
            n[cnt] = 0;
            while (a % pr[i] == 0) a /= pr[i], n[cnt]++;
            cnt++;
        }
        i++;
    }
    if (a != 1) f[cnt] = a, n[cnt++] = 1;
}

int cnt_fac(int n, int f){
    int ep = f;
    int ret = 0;

    while (ep <= n){
        ret += n / ep;
        ep *= f;
    }

    return ret;
}

bool deal(int a, int b){
    int f[30], cf[30];
    int n = 0;

    memset(f, 0, sizeof(f));
    fac(a, f, cf, n);
    #if debug
    printf("n  %d\n\n", n);
    for (int i = 0; i < n; i++) {
        printf("%d  %d\n", f[i], cf[i]);
    }
    f[n] = 0;
    #endif

    for (int i = 0; i < n; i++) {
        #if debug
        printf("fac %d  num %d\n", f[i], cnt_fac(b, f[i]));
        #endif
        if (cf[i] > cnt_fac(b, f[i])) {
            return false;
        }
    }
    return true;
}

int main(){
    int a, b;

    gp();
    while (~scanf("%d%d", &a, &b)){
        if (deal(b, a) && b) {
            printf("%d divides %d!\n", b, a);
        }
        else {
            printf("%d does not divide %d!\n", b, a);
        }
    }

    return 0;
}

　

——written by Lyon