D - Progressions Covering

https://codeforces.com/contest/1661/submission/153215303

Codeforces/1661/D/D.cpp

@@ -0,0 +1,100 @@
+#include <cmath>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 3e5 + 5;
+
+struct node {
+    int l, r;
+    long long s, d;
+
+    node()
+        : l(0), r(0), s(0), d(0) {}
+    node(int _l, int _r)
+        : l(_l), r(_r), s(0), d(0) {}
+} tr[N << 2];
+
+int n, k;
+long long x, t, ans, a[N], b[N];
+bool flag[N];
+
+inline void pushup(int u) {
+    tr[u].s = tr[u << 1].s + tr[u << 1 | 1].s;
+}
+
+inline void pushdown(int u) {
+    tr[u << 1].s += (tr[u << 1].r - tr[u << 1].l + 1) * tr[u].d;
+    tr[u << 1].d += tr[u].d;
+    tr[u << 1 | 1].s += (tr[u << 1 | 1].r - tr[u << 1 | 1].l + 1) * tr[u].d;
+    tr[u << 1 | 1].d += tr[u].d;
+    tr[u].d = 0;
+}
+
+void build(int u, int l, int r) {
+    tr[u] = node(l, r);
+    if (l == r) {
+        tr[u].s = b[l];
+        return;
+    }
+    int mid = l + r >> 1;
+    build(u << 1, l, mid);
+    build(u << 1 | 1, mid + 1, r);
+    pushup(u);
+}
+
+void modify(int u, int l, int r, long long d) {
+    if (l <= tr[u].l && tr[u].r <= r) {
+        tr[u].s += (tr[u].r - tr[u].l + 1) * d;
+        tr[u].d += d;
+        return;
+    }
+    pushdown(u);
+    int mid = tr[u].l + tr[u].r >> 1;
+    if (l <= mid) modify(u << 1, l, r, d);
+    if (r > mid) modify(u << 1 | 1, l, r, d);
+    pushup(u);
+}
+
+long long query(int u, int l, int r) {
+    if (l <= tr[u].l && tr[u].r <= r) {
+        return tr[u].s;
+    }
+    pushdown(u);
+    int mid = tr[u].l + tr[u].r >> 1;
+    long long sum = 0;
+    if (l <= mid) sum += query(u << 1, l, r);
+    if (r > mid) sum += query(u << 1 | 1, l, r);
+    return sum;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n >> k;
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+        b[i] = a[i] - a[i - 1];
+    }
+
+    build(1, 1, n);
+
+    for (int i = n; i >= k; i--) {
+        if ((t = query(1, 1, i)) > 0) {
+            x = std::ceil(1.0 * t / k);
+            modify(1, i - k + 1, i, -x);
+            ans += x;
+        }
+    }
+
+    t = 0;
+    for (int i = 1; i < k; i++) {
+        t = std::max(t, (long long)ceil(1.0 * query(1, 1, i) / i));
+    }
+
+    cout << ans + t << endl;
+
+    return 0;
+}