154 lines
3.1 KiB
C++
154 lines
3.1 KiB
C++
#include <bits/stdc++.h> // {{{
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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template <typename T>
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constexpr T MIN = std::numeric_limits<T>::min();
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template <typename T>
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constexpr T MAX = std::numeric_limits<T>::max();
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template <typename T>
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[[nodiscard]] static T sc(auto&& x) {
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return static_cast<T>(x);
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}
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template <typename T>
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[[nodiscard]] static T sz(auto&& x) {
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return static_cast<T>(x.size());
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}
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#define prln(...) std::println(__VA_ARGS__)
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#define pr(...) std::print(__VA_ARGS__)
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#ifdef LOCAL
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#define dbgln(...) std::println(__VA_ARGS__)
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#define dbg(...) std::print(__VA_ARGS__)
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#endif
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using ll = long long;
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using ld = long double;
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template <typename T>
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using v = std::vector<T>;
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template <typename T, size_t N>
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using r = std::array<T, N>;
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template <typename T1, typename T2>
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using p = std::pair<T1, T2>;
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#define ff first
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#define ss second
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#define eb emplace_back
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#define pb push_back
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#define all(x) (x).begin(), (x).end()
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#define rall(x) (x).rbegin(), (x).rend()
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// }}}
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template <typename T>
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struct fenwick_tree {
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public:
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explicit fenwick_tree(std::vector<T> const& ts) : tree(ts.size()) {
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for (size_t i = 0; i < ts.size(); ++i) {
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tree[i] = ts[i];
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}
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for (size_t i = 0; i < tree.size(); ++i) {
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size_t j = g(i);
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if (j < tree.size()) {
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tree[j] += tree[i];
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}
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}
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}
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T const query(size_t i) const {
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if (!(0 <= i && i < tree.size())) {
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throw std::out_of_range(std::format(
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"cannot query fenwick tree of size {} at index {}", tree.size(), i));
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}
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T t = sentinel();
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for (int j = static_cast<int>(i); j >= 0; j = h(j) - 1) {
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t = merge(t, tree[j]);
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}
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return t;
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};
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T const query(size_t l, size_t r) const {
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if (!(0 <= l && r < tree.size())) {
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throw std::out_of_range(
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std::format("cannot query fenwick tree of size {} at range [{}, {}]",
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tree.size(), l, r));
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}
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if (l == 0) {
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return query(r);
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}
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return unmerge(query(r), query(l - 1));
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};
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void update(size_t i, T const& t) noexcept {
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assert(0 <= i && t < tree.size());
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for (size_t j = i; j < tree.size(); j = g(j)) {
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tree[j] = merge(tree[j], t);
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}
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}
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private:
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[[nodiscard]] inline T merge(T const& x, T const& y) const noexcept {
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return x + y;
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}
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[[nodiscard]] inline T unmerge(T const& x, T const& y) const noexcept {
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return x - y;
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}
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[[nodiscard]] inline T sentinel() const noexcept {
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return 0;
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}
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[[nodiscard]] inline size_t g(size_t i) const noexcept {
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return i | (i + 1);
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}
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[[nodiscard]] size_t h(size_t i) const noexcept {
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return i & (i + 1);
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}
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std::vector<T> tree;
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};
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void solve() {
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int n, q;
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cin >> n >> q;
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v<ll> a(n);
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for (auto& e : a)
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cin >> e;
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fenwick_tree<ll> fw(a);
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while (q--) {
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ll l, r;
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cin >> l >> r;
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--l;
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--r;
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cout << fw.query(l, r) << endl;
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}
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}
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int main() { // {{{
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cin.tie(nullptr)->sync_with_stdio(false);
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int t = 1;
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// cin >> t;
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while (t--) {
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solve();
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}
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return 0;
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}
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// }}}
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