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https://git.sb/baoshuo/OI-codes.git
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78 lines
1.6 KiB
C++
78 lines
1.6 KiB
C++
#include <iostream>
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#include <algorithm>
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#include <cmath>
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#include <tuple>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 50005;
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int n, m, a[N], c[N], t;
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std::pair<long long, long long> now, ans[N];
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std::vector<std::tuple<int, int, int>> q;
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void add(int x) {
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if (++c[x] > 1) {
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now.first += c[x] * (c[x] - 1) - (c[x] - 1) * (c[x] - 2);
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}
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}
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void del(int x) {
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if (--c[x]) {
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now.first += c[x] * (c[x] - 1) - (c[x] + 1) * c[x];
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}
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> m;
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t = sqrt(n);
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for (int i = 1; i <= n; i++) {
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cin >> a[i];
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}
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for (int i = 1, l, r; i <= m; i++) {
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cin >> l >> r;
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q.push_back(std::make_tuple(i, l, r));
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}
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std::sort(q.begin(), q.end(), [&](auto a, auto b) {
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int p = std::get<1>(a) / t,
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q = std::get<1>(b) / t;
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return p == q ? std::get<2>(a) < std::get<2>(b) : p < q;
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});
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int i = 0, j = 1, x, l, r;
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for (auto e : q) {
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std::tie(x, l, r) = e;
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if (l == r) {
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ans[x] = std::make_pair(0, 1);
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} else {
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while (i < r) add(a[++i]);
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while (i > r) del(a[i--]);
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while (j < l) del(a[j++]);
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while (j > l) add(a[--j]);
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now.second = 1ll * (r - l + 1) * (r - l);
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int g = std::__gcd(now.first, now.second);
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ans[x] = std::make_pair(now.first / g, now.second / g);
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}
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}
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for (int i = 1; i <= m; i++) {
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cout << ans[i].first << '/' << ans[i].second << endl;
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}
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return 0;
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}
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