#2880. 「JOISC 2014 Day3」稻草人

https://loj.ac/s/1581327

LibreOJ/2880/2880.cpp

@@ -0,0 +1,112 @@
+#include <iostream>
+#include <algorithm>
+#include <limits>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 2e5 + 5;
+
+int n, c[N], st[N];
+long long ans;
+std::vector<int> xs;
+std::pair<int, int> p[N];
+
+inline int lowbit(int x) {
+    return x & -x;
+}
+
+void insert(int x, int y) {
+    for (; x; x -= lowbit(x)) c[x] = std::min(c[x], y);
+}
+
+int query(int x) {
+    int res = std::numeric_limits<int>::max();
+
+    for (; x <= n; x += lowbit(x)) res = std::min(res, c[x]);
+
+    return res;
+}
+
+void clear(int x) {
+    for (; x; x -= lowbit(x)) c[x] = std::numeric_limits<int>::max();
+}
+
+int search(int l, int r, int y) {
+    int res = r + 1;
+
+    while (l <= r) {
+        int mid = l + r >> 1;
+
+        if (p[st[mid]].second < y) {
+            res = mid;
+            r = mid - 1;
+        } else {
+            l = mid + 1;
+        }
+    }
+
+    return res;
+}
+
+void solve(int l, int r) {
+    if (l >= r) return;
+
+    int mid = (l + r) >> 1;
+    solve(l, mid);
+    solve(mid + 1, r);
+
+    for (int i = l, j = mid + 1, top = 0; i <= mid; i++) {
+        while (j <= r && p[j].second > p[i].second) {
+            while (top && p[st[top]].first > p[j].first) top--;
+
+            st[++top] = j++;
+        }
+
+        ans += top - search(1, top, query(p[i].first)) + 1;
+
+        insert(p[i].first, p[i].second);
+    }
+
+    for (int i = l; i <= mid; i++) {
+        clear(p[i].first);
+    }
+
+    std::sort(p + l, p + r + 1, [](const std::pair<int, int> &a, const std::pair<int, int> &b) {
+        return a.second > b.second;
+    });
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    std::fill_n(c, N, std::numeric_limits<int>::max());
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> p[i].first >> p[i].second;
+
+        xs.emplace_back(p[i].first);
+    }
+
+    std::sort(p + 1, p + 1 + n, [](const std::pair<int, int> &a, const std::pair<int, int> &b) {
+        return a.first < b.first;
+    });
+    std::sort(xs.begin(), xs.end());
+    xs.erase(std::unique(xs.begin(), xs.end()), xs.end());
+
+    for (int i = 1; i <= n; i++) {
+        p[i].first = std::lower_bound(xs.begin(), xs.end(), p[i].first) - xs.begin() + 1;
+    }
+
+    solve(1, n);
+
+    cout << ans << endl;
+
+    return 0;
+}