163. 生日礼物

https://www.acwing.com/problem/content/submission/code_detail/17825641/

AcWing/163/163.cpp

@@ -0,0 +1,80 @@
+#include <iostream>
+#include <cmath>
+#include <functional>
+#include <queue>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n, m, p = 1, a[N], pre[N], suf[N], ans;
+bool vis[N];
+std::priority_queue<
+    std::pair<int, int>,
+    std::vector<std::pair<int, int>>,
+    std::greater<>>
+    q;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1, x; i <= n; i++) {
+        cin >> x;
+
+        if (a[p] * x < 0) {
+            a[++p] = x;
+        } else {
+            a[p] += x;
+        }
+    }
+
+    int cnt = 0;
+    for (int i = 1; i <= p; i++) {
+        pre[i] = i - 1;
+        suf[i] = i + 1;
+
+        if (a[i] > 0) {
+            ans += a[i];
+            cnt++;
+        }
+
+        q.emplace(std::abs(a[i]), i);
+    }
+
+    while (cnt > m) {
+        while (vis[q.top().second]) q.pop();
+
+        auto o = q.top();
+        q.pop();
+
+        if (pre[o.second] != 0 && suf[o.second] != p + 1 || a[o.second] > 0) {
+            cnt--;
+            ans -= o.first;
+
+            int l = pre[o.second],
+                r = suf[o.second];
+
+            a[o.second] += a[l] + a[r];
+            q.emplace(std::abs(a[o.second]), o.second);
+
+            pre[suf[l]] = pre[l];
+            suf[pre[l]] = suf[l];
+            vis[l] = true;
+
+            pre[suf[r]] = pre[r];
+            suf[pre[r]] = suf[r];
+            vis[r] = true;
+        }
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}