Ural1049

get_prime函数可作为O(n)打素数表的模板 附带因子分解功能

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

const int MAXN = 10010, N = 10000;

int pn = 0, prime[MAXN], factor[MAXN], ansfactor[MAXN];

void get_prime(int n)
{
for (int i = 1; i <= n; i++)
factor[i] = i;
for (int i = 2; i <= n; i++)
{
if (i == factor[i])
prime[pn++] = i;
for (int j = 0; j < pn && prime[j] * i <= n; j++)
{
factor[i * prime[j]] = prime[j];
if (i % prime[j] == 0)
break;
}
}
}

int main()
{
get_prime(N);

int a, ans = 1;
for (int i = 0; i < 10; i++)
{
scanf("%d", &a);
while (a != 1)
{
ansfactor[factor[a]]++;
a /= factor[a];
}
}
for (int i = 0; i < pn; i++)
if (ansfactor[prime[i]] > 0)
{
ans = ans * (ansfactor[prime[i]] + 1) % 10;
}
printf("%d\n", ans);

return 0;
}