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| #include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
const int N = 5e4 + 10;
typedef long long LL;
int n, m, len, c[N], cnt[N];
LL sum, ans1[N], ans2[N];
struct query
{
int l, r, id;
bool operator<(const query &x) const
{
if (l / len != x.l / len)
return l < x.l;
return (l / len) & 1 ? r < x.r : r > x.r;
}
} q[N];
void add(int i)
{
sum += cnt[i];
cnt[i]++;
}
void del(int i)
{
cnt[i]--;
sum -= cnt[i];
}
LL gcd(LL a, LL b)
{
return b ? gcd(b, a % b) : a;
}
int main()
{
scanf("%d%d", &n, &m);
len = sqrt(n);
for (int i = 1; i <= n; i++)
scanf("%d", &c[i]);
for (int i = 0; i < m; i++)
{
scanf("%d%d", &q[i].l, &q[i].r);
q[i].id = i;
}
sort(q, q + m);
for (int i = 0, l = 1, r = 0; i < m; i++)
{
if (q[i].l == q[i].r)
{
ans1[q[i].id] = 0;
ans2[q[i].id] = 1;
continue;
}
while (l > q[i].l)
add(c[--l]);
while (r < q[i].r)
add(c[++r]);
while (l < q[i].l)
del(c[l++]);
while (r > q[i].r)
del(c[r--]);
ans1[q[i].id] = sum;
ans2[q[i].id] = (LL)(r - l + 1) * (r - l) / 2;
}
for (int i = 0; i < m; i++)
{
if (ans1[i])
{
LL g = gcd(ans1[i], ans2[i]);
ans1[i] /= g, ans2[i] /= g;
}
else
ans2[i] = 1;
printf("%lld/%lld\n", ans1[i], ans2[i]);
}
return 0;
}
|