new file: P2048.cpp

P2048.cpp

@@ -0,0 +1,72 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int MAXN = 500005;
+const int LOG = 20;
+int n, k, L, R;
+long long pre[MAXN];
+int lg2[MAXN];
+int st[LOG][MAXN];
+int query(int l, int r) {
+    int len = r - l + 1;
+    int t = lg2[len];
+    int x = st[t][l];
+    int y = st[t][r - (1 << t) + 1];
+    return pre[x] <= pre[y] ? x : y;
+}
+struct Node {
+    long long val;
+    int r, ql, qr, pos;
+    bool operator<(const Node &other) const { return val < other.val; }
+};
+int main() {
+    scanf("%d %d %d %d", &n, &k, &L, &R);
+    for (int i = 1; i <= n; ++i) {
+        int x;
+        scanf("%d", &x);
+        pre[i] = pre[i - 1] + x;
+    }
+    int m = n + 1;
+    lg2[1] = 0;
+    for (int i = 2; i <= m; ++i) {
+        lg2[i] = lg2[i / 2] + 1;
+    }
+    for (int i = 0; i < m; ++i) {
+        st[0][i] = i;
+    }
+    for (int j = 1; (1 << j) <= m; ++j) {
+        for (int i = 0; i + (1 << j) <= m; ++i) {
+            int x = st[j - 1][i];
+            int y = st[j - 1][i + (1 << (j - 1))];
+            st[j][i] = (pre[x] <= pre[y] ? x : y);
+        }
+    }
+    priority_queue<Node> pq;
+    for (int r = 1; r <= n; ++r) {
+        int ql = max(0, r - R);
+        int qr = r - L;
+        if (ql <= qr) {
+            int pos = query(ql, qr);
+            pq.push({pre[r] - pre[pos], r, ql, qr, pos});
+        }
+    }
+    long long ans = 0;
+    for (int cnt = 0; cnt < k && !pq.empty(); ++cnt) {
+        Node cur = pq.top();
+        pq.pop();
+        ans += cur.val;
+        int r = cur.r;
+        int ql = cur.ql;
+        int qr = cur.qr;
+        int pos = cur.pos;
+        if (ql <= pos - 1) {
+            int np = query(ql, pos - 1);
+            pq.push({pre[r] - pre[np], r, ql, pos - 1, np});
+        }
+        if (pos + 1 <= qr) {
+            int np = query(pos + 1, qr);
+            pq.push({pre[r] - pre[np], r, pos + 1, qr, np});
+        }
+    }
+    printf("%lld\n", ans);
+    return 0;
+}