P4105 [HEOI2014] 南园满地堆轻絮

https://www.luogu.com.cn/record/85674001

Luogu/P4105/P4105.cpp

@@ -0,0 +1,58 @@
+#include <iostream>
+#include <algorithm>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 5e6 + 5;
+
+int n, s_a, s_b, s_c, s_d, a[N], b[N], mod, ans;
+
+inline int f(int x) {
+    return (static_cast<long long>(s_a) % mod * x % mod * x % mod * x % mod
+            + static_cast<long long>(s_b) % mod * x % mod * x % mod
+            + static_cast<long long>(s_c) % mod * x % mod
+            + s_d)
+         % mod;
+}
+
+bool check(int x) {
+    std::copy_n(a + 1, n, b + 1);
+
+    for (int i = 1; i <= n; i++) {
+        b[i] = std::max(b[i - 1], b[i] - x);
+
+        if (std::abs(a[i] - b[i]) > x) return false;
+    }
+
+    return true;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> s_a >> s_b >> s_c >> s_d >> a[1] >> mod;
+
+    for (int i = 2; i <= n; i++) {
+        a[i] = (f(a[i - 1]) + f(a[i - 2])) % mod;
+    }
+
+    int l = 0, r = mod;
+
+    while (l <= r) {
+        int mid = l + r >> 1;
+
+        if (check(mid)) {
+            ans = mid;
+            r = mid - 1;
+        } else {
+            l = mid + 1;
+        }
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}