Submission #400183

#	Time	Username	Problem	Language	Result	Execution time	Memory
400183		hltk	Harbingers (CEOI09_harbingers)	C++17	100 / 100	149 ms	17500 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) {
		dp[u] = cd * t[u] + s[u] - 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 = bins(0, ed - 1, [&](int m) {
			return intersect(cht[m], cht[m + 1]) >= intersect(cht[m + 1], l);
		}) + 1;
		swap(cht[ned], 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:46:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   46 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
harbingers.cpp:48:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   48 |   scanf("%d %d %d", &u, &v, &d);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
harbingers.cpp:52:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   52 |  for (int i = 2; i <= n; ++i) scanf("%d %d", s + i, t + i);
      |                               ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 100 / 100