HDU-5514-Frogs

描述

题解

代码

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

typedef long long ll;

const ll MAXN = 1e4 + 5;

ll gcd(ll a, ll b)
{
if (b == 0)
{
return a;
}
return gcd(b, a % b);
}

int n;
ll m;
ll a[MAXN];
ll g[MAXN];
ll fac[MAXN];

ll Phi(ll x)
{
ll ans = x;
for (ll i = 2; i * i <= x; i++)
{
if (x % i == 0)
{
ans -= ans / i;
while (x % i == 0)
{
x /= i;
}
}
}

if (x > 1)
{
ans -= ans/x;
}
return ans;
}

int main()
{
int T;
scanf("%d", &T);

for (int ce = 1; ce <= T; ce++)
{
scanf("%d%lld", &n, &m);

int flag = 0;
for (int i = 0; i < n; i++)
{
scanf("%lld", a + i);

g[i] = gcd(a[i], m);
if (g[i] == 1)
{
flag = 1;
}
}

printf("Case #%d: ", ce);
if (flag == 1)
{
printf("%lld\n", m * (m - 1) >> 1);
continue;
}

sort(g, g + n);
n = (int)(unique(g, g + n) - g);

int cnt = 0;
for (ll i = 2; i * i <= m; i++)
{
if (i * i == m)
{
fac[cnt++] = m / i;
}
else if (m % i == 0)
{
fac[cnt++] = i;
fac[cnt++] = m / i;
}
}
sort(fac, fac + cnt);

ll sum = 0;
for (int i = 0; i < cnt; i++)
{
for (int j = 0; j < n; j++)
{
if (fac[i] % g[j] == 0)
{
sum += Phi(m / fac[i]) * m >> 1;
break;
}
}
}

printf("%lld\n", sum);
}

return 0;
}