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CSES Problem Set/Visible Buildings Queries.cpp

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+/* Problem URL: https://cses.fi/problemset/task/3304 */
+
+#include <bits/stdc++.h>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+
+using namespace std;
+using namespace __gnu_pbds;
+
+template <class T, class comp = less<>>
+using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (int i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int n, q;
+    cin >> n >> q;
+
+    vl fds(n);
+    cin >> fds;
+
+    vvi sparse(20, vi(n));
+
+    rep(i, n) {
+        sparse[0][i] = fds[i];
+    }
+
+    nrep(j, 1, 20) {
+        for (int i = 0; i + (1 << (j - 1)) < n; i++) {
+            sparse[j][i] = max(sparse[j - 1][i], sparse[j - 1][i + (1 << (j - 1))]);
+        }
+    }
+
+    auto squery = [&](int i, int j) {
+        int log = 31 - __builtin_clz(j - i + 1);
+
+        return max(sparse[log][i], sparse[log][j - (1 << log) + 1]);
+    };
+
+    vi ans(n);
+
+    rep(i, n) {
+        int low = 0;
+        int high = i - 1;
+        int act = i;
+
+        while (low <= high) {
+            int mid = (low + high) >> 1;
+
+            if (squery(mid, i - 1) < fds[i]) {
+                act = mid;
+                high = mid - 1;
+                continue;
+            }
+
+            low = mid + 1;
+        }
+
+        ans[i] = act;
+    }
+
+
+    int oo = INT32_MAX >> 1;
+
+    while (__builtin_popcount(n) != 1) {
+        n++;
+        ans.push_back(oo);
+    }
+
+    vvi mergeseg(n * 2);
+
+    function<void(int, int, int)> build = [&](int i, int l, int r) {
+        if (l == r) {
+            mergeseg[i] = {ans[i - n]};
+            return;
+        }
+
+        int mid = (l + r) >> 1;
+
+        build(i * 2, l, mid);
+        build(i * 2 + 1, mid + 1, r);
+
+        merge(all(mergeseg[i * 2]), all(mergeseg[i * 2 + 1]), back_inserter(mergeseg[i]));
+    };
+
+    build(1, 0, n - 1);
+
+    function<int(int, int, int, int, int, int)> query = [&](int i, int l, int r, int tl, int tr, int v) -> int {
+        if (l > tr || r < tl) {
+            return 0;
+        }
+
+        if (l >= tl && r <= tr) {
+            auto upper = upper_bound(all(mergeseg[i]), v);
+
+            return upper - mergeseg[i].begin();
+        }
+
+        int mid = (l + r) >> 1;
+
+        return query(i * 2, l, mid, tl, tr, v) + query(i * 2 + 1, mid + 1, r, tl, tr, v);
+    };
+
+    while (q--) {
+        int a, b;
+        cin >> a >> b;
+        a--, b--;
+
+        cout << query(1, 0, n - 1, a, b, a) << '\n';
+    }
+}