Submission #426771

#	Time	Username	Problem	Language	Result	Execution time	Memory
426771		LittlePants	Race (IOI11_race)	C++17	21 / 100	3046 ms	29856 KiB

race

#include "race.h"
#include<bits/stdc++.h>
#define pb push_back
#define eb emplace_back
#define push emplace
#define lb(x, v) lower_bound(all(x), v)
#define ub(x, v) upper_bound(all(x), v)
#define sz(x) (int)(x.size())
#define re(x) reverse(all(x))
#define uni(x) x.resize(unique(all(x)) - x.begin())
#define all(x) x.begin(), x.end()
#define mem(x, v) memset(x, v, sizeof x); 
#define pii pair<int, int>
#define inf 1e9
#define INF 1e18
#define mod 1000000007
#define F first
#define S second
#define IO ios_base::sync_with_stdio(0); cin.tie(0);
#define chmax(a, b) (a = (b > a ? b : a))
#define chmin(a, b) (a = (b < a ? b : a))
using namespace std;

void trace_() {cerr << "\n";}
template<typename T1, typename... T2> void trace_(T1 t1, T2... t2) {cerr << ' ' << t1; trace_(t2...); }
#define trace(...) cerr << "[" << #__VA_ARGS__ << "] :", trace_(__VA_ARGS__);

const int mxN = 2e5 + 5;
int n, k, ans = inf, sz[mxN], bson[mxN], bw[mxN];
vector<pii> g[mxN];

void pre(int u, int p) {
	sz[u] = 1;
	int id = -1, ww = 0;
	for (auto [v, w] : g[u]) {
		if (v == p) continue;
		pre(v, u);
		sz[u] += sz[v];
		if (id == -1 or sz[id] < sz[v]) id = v, ww = w;
	}
	bson[u] = id;
	bw[u] = ww;
}

map<int, int> dfs(int u, int p) {
	map<int, int> mp, t;
	if (~bson[u]) t = dfs(bson[u], u);
	for (auto [len, step] : t) mp[len + bw[u]] = step + 1;
	mp[0] = 0;

	for (auto [v, w] : g[u]) {
		if (v == bson[u] or v == p) continue;	
		t = dfs(v, u);
		for (auto [len, step] : t) {
			if (len + w <= k and mp.count(k - len - w)) {
				ans = min(ans, mp[k - len - w] + step + 1);
			}
			if (mp.count(len + w)) {
				mp[len + w] = min(mp[len + w], step + 1);
			} else {
				mp[len + w] = step + 1;
			}
		}
	}
	if (mp.count(k)) {
		ans = min(ans, mp[k]);
	}

	return mp;
}

int best_path(int N, int K, int H[][2], int L[]) {
	n = N; k = K;
	for (int i = 0; i < n - 1; i ++) {
		g[H[i][0]].pb({H[i][1], L[i]});
		g[H[i][1]].pb({H[i][0], L[i]});
	}

	mem(bson, -1);
	pre(0, -1);
	dfs(0, -1);

	if (ans > n) ans = -1;
	return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57