P1484 种树

https://www.luogu.com.cn/record/99833486

Luogu/P1484/P1484.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+#include <queue>
+#include <utility>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 5e5 + 5;
+
+int n, k, a[N << 1], l[N << 1], r[N << 1];
+long long ans;
+std::priority_queue<std::pair<int, int>> q;
+bool vis[N << 1];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+
+        q.emplace(a[i], i);
+        l[i] = i - 1;
+        r[i] = i + 1;
+    }
+
+    for (int i = 1, cnt = n; i <= k; i++) {
+        while (!q.empty() && vis[q.top().second]) q.pop();
+
+        if (q.empty() || q.top().first < 0) break;
+
+        int id = q.top().second;
+        ans += q.top().first;
+        q.pop();
+
+        vis[id] = vis[l[id]] = vis[r[id]] = true;
+        a[++cnt] = a[l[id]] + a[r[id]] - a[id];
+        l[cnt] = l[l[id]], r[cnt] = r[r[id]];
+        r[l[cnt]] = cnt, l[r[cnt]] = cnt;
+
+        q.emplace(a[cnt], cnt);
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}