P3620 [APIO/CTSC2007] 数据备份

https://www.luogu.com.cn/record/88613869

Luogu/P3620/P3620.cpp

@@ -0,0 +1,72 @@
+#include <iostream>
+#include <limits>
+#include <queue>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 100005;
+
+int n, k, a[N], pre[N], suf[N];
+long long c[N], ans;
+std::priority_queue<
+    std::pair<int, long long>,
+    std::vector<std::pair<int, long long>>,
+    auto(*)(std::pair<int, long long>, std::pair<int, long long>)->bool>
+q([](std::pair<int, long long> a, std::pair<int, long long> b) -> bool {
+    return a.second > b.second;
+});
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+
+    for (int i = 1; i < n; i++) {
+        c[i] = static_cast<long long>(a[i + 1]) - a[i];
+        pre[i] = i - 1;
+        suf[i] = i + 1;
+    }
+    suf[n - 1] = 0;
+
+    for (int i = 1; i < n; i++) {
+        q.emplace(i, c[i]);
+    }
+
+    while (k--) {
+        auto o = q.top();
+        q.pop();
+
+        if (o.second != c[o.first]) {
+            k++;
+
+            continue;
+        }
+
+        ans += o.second;
+
+        int l = pre[o.first],
+            r = suf[o.first];
+
+        suf[o.first] = suf[r];
+        pre[suf[o.first]] = o.first;
+        pre[o.first] = pre[l];
+        suf[pre[o.first]] = o.first;
+
+        c[o.first] = (l && r) ? std::min(static_cast<long long>(std::numeric_limits<int>::max()), c[l] + c[r] - c[o.first]) : std::numeric_limits<int>::max();
+        c[l] = c[r] = std::numeric_limits<int>::max();
+
+        q.emplace(o.first, c[o.first]);
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}