Submission #400180

#	Time	Username	Problem	Language	Result	Execution time	Memory
400180		hltk	Harbingers (CEOI09_harbingers)	C++17	50 / 100	1097 ms	19884 KiB

harbingers

#include <bits/stdc++.h>
using namespace std;
// template <typename T>
// int bins(int l, int r, T f) {
// 	while (l < r) {
// 		int m = (l + r) / 2;
// 		f(m) ? r = m : l = m + 1;
// 	}
// 	return l;
// }
const long INF = 1e18;
int n, s[100100], t[100100];
long dp[100100];
vector<pair<int, int>> g[100100];
struct Line {
	long m, c;
	long operator()(long x) { return m * x + c; }
} cht[100100];
long intersect(Line a, Line b) {
	long num = b.c - a.c, dem = a.m - b.m;
	return num / dem - ((num ^ dem) < 0 && num % dem);
}
void dfs(int u, int p, int ed, long cd) {
	if (u != 1) {
		long r = -INF;
		for (int i = 0; i < ed; ++i) r = max(r, cht[i](t[u]));
		dp[u] = cd * t[u] + s[u] - r /* cht[bins(0, ed - 1, [&](int m) {
			return cht[m](t[u]) > cht[m + 1](t[u]);
		})](t[u])*/;
		Line l{cd, -dp[u]};
		int ned = 0;
		while (ned + 1 < ed) {
			if (intersect(cht[ned], cht[ned + 1]) < intersect(cht[ned + 1], l)) {
				ned++;
			} else break;
		}
		ned++;
		swap(cht[ned], l);
		// bins(0, ed - 1, [&](int m) {
		// 	return intersect(cht[m], cht[m + 1]) >= intersect(cht[m + 1], l);
		// });
		for (auto [v, d] : g[u]) {
			if (v == p) continue;
			dfs(v, u, ned + 1, cd + d);
		}
		swap(cht[ned], l);
	} else {
		for (auto [v, d] : g[u]) {
			if (v == p) continue;
			dfs(v, u, ed, cd + d);
		}
	}
}
int main() {
	scanf("%d", &n);
	for (int i = 1, u, v, d; i <= n - 1; ++i) {
		scanf("%d %d %d", &u, &v, &d);
		g[u].emplace_back(v, d);
		g[v].emplace_back(u, d);
	}
	for (int i = 2; i <= n; ++i) scanf("%d %d", s + i, t + i);
	dfs(1, -1, 1, 0);
	for (int i = 2; i <= n; ++i) printf("%ld%c", dp[i], i == n ? '\n' : ' ');
}
// f_j(x) := -dp[j] + dep[j] * x
//   dp[j] + (d - x) t_i + s_i
// = dp[j] - x * t_i + d * t_i + s_i
// = -f_j(t_i) + d * t_i + s_i

Compilation message (stderr)

harbingers.cpp: In function 'int main()':
harbingers.cpp:55:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   55 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
harbingers.cpp:57:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   57 |   scanf("%d %d %d", &u, &v, &d);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
harbingers.cpp:61:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   61 |  for (int i = 2; i <= n; ++i) scanf("%d %d", s + i, t + i);
      |                               ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 50 / 100