P3157 [CQOI2011]动态逆序对

https://www.luogu.com.cn/record/76372007

Luogu/P3157/P3157.cpp

@@ -0,0 +1,118 @@
+#include <algorithm>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n, m, pos[N];
+long long c[N], ans[N];
+
+struct node {
+    int t, i, v;
+
+    node() {}
+
+    node(int _t, int _i, int _v)
+        : t(_t), i(_i), v(_v) {}
+
+    bool operator<(const node& x) {
+        return i == x.i ? v < x.v : i < x.i;
+    }
+} q[N], w[N];
+
+inline int lowbit(int x) {
+    return x & -x;
+}
+
+void add(int x, int y) {
+    for (; x <= n; x += lowbit(x)) c[x] += y;
+}
+
+int sum(int x) {
+    int res = 0;
+    for (; x; x -= lowbit(x)) res += c[x];
+    return res;
+}
+
+void solve(int l, int r) {
+    if (l >= r) return;
+
+    int mid = l + r >> 1;
+
+    solve(l, mid);
+    solve(mid + 1, r);
+
+    int i = l, j = mid + 1, k = 0;
+    while (i <= mid && j <= r) {
+        if (q[i] < q[j]) {
+            add(q[i].v, 1);
+            w[++k] = q[i++];
+        } else {
+            ans[q[j].t] += sum(n) - sum(q[j].v);
+            w[++k] = q[j++];
+        }
+    }
+
+    while (i <= mid) {
+        add(q[i].v, 1);
+        w[++k] = q[i++];
+    }
+
+    while (j <= r) {
+        ans[q[j].t] += sum(n) - sum(q[j].v);
+        w[++k] = q[j++];
+    }
+
+    for (int i = l; i <= mid; i++) add(q[i].v, -1);
+    for (int i = l, j = 1; j <= k; i++, j++) q[i] = w[j];
+
+    for (int i = r; i >= l; i--) {
+        if (q[i].t <= mid) {
+            add(q[i].v, 1);
+        } else {
+            ans[q[i].t] += sum(q[i].v);
+        }
+    }
+
+    for (int i = r; i >= l; i--) {
+        if (q[i].t <= mid) add(q[i].v, -1);
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n >> m;
+
+    for (int i = 1, x; i <= n; i++) {
+        cin >> x;
+        pos[x] = i;
+        q[i] = node(0, i, x);
+    }
+
+    int t = n;
+    for (int i = 1, x; i <= m; i++) {
+        cin >> x;
+        q[pos[x]].t = t--;
+    }
+    for (int i = 1; i <= n; i++) {
+        if (!q[i].t) q[i].t = t--;
+    }
+
+    std::sort(q + 1, q + 1 + n, [&](const node& a, const node& b) {
+        return a.t < b.t;
+    });
+
+    solve(1, n);
+
+    for (int i = 1; i <= n; i++) ans[i] += ans[i - 1];
+
+    for (int i = n; i > n - m; i--) {
+        cout << ans[i] << endl;
+    }
+
+    return 0;
+}