Submission #306341

#	Time	Username	Problem	Language	Result	Execution time	Memory
306341		syy	Race (IOI11_race)	C++17	100 / 100	742 ms	35692 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define FOR(i, a, b) for(int i = (int)a; i <= (int)b; i++)
#define DEC(i, a, b) for(int i = (int)a; i >= (int)b; i--)
typedef pair<int, int> pi;
typedef pair<int, pi> pii;
typedef pair<pi, pi> pipi;
#define f first
#define s second
typedef vector<int> vi;
typedef vector<pi> vpi;
typedef vector<pii> vpii;
#define pb push_back
#define pf push_front
#define all(v) v.begin(), v.end()
#define disc(v) sort(all(v)); v.resize(unique(all(v)) - v.begin());
#define INF (int) 1e9 + 100
#define LLINF (ll) 1e18
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)

int n, k, sz[200005], coun, ans = INF;
int newdist[1000005], dist[1000005];
bool vis[200005];
vpi adj[200005];

int sztrsz(int x, int p) {
	sz[x] = 1;
	for (auto it:adj[x]) if (!vis[it.f] and it.f != p) sz[x] += sztrsz(it.f, x);
	return sz[x];
}

int findcent(int x, int p, int n) {
	for (auto it:adj[x]) {
		if (vis[it.f]) continue;
		if (it.f != p and sz[it.f] > n/2 and !vis[it.f]) return findcent(it.f, x, n);
	}
	return x;
}

void dfsend(int x, int p, int d, int num) {
	if (d == k) ans = min(ans, num);
	if (d > k) return;
	for (auto it:adj[x]) if (!vis[it.f] and it.f != p) dfsend(it.f, x, d+it.s, num+1);
}

vi cur, temp;

void dfs(int x, int p, int d, int num) {
	if (d == k) ans = min(ans, num);
	if (d > k) return;
	if (dist[k-d] != INF) ans = min(ans, num + dist[k-d]);
	newdist[d] = min(newdist[d], num);
	cur.pb(d); temp.pb(d);
	for (auto it:adj[x]) if (it.f != p and !vis[it.f]) dfs(it.f, x, d + it.s, num+1);
}

void solve(int x) {
	int cent = findcent(x, -1, sztrsz(x, -1));
	dfsend(cent, -1, 0, 0);
	for (auto it:adj[cent]) if (!vis[it.f]) {
		dfs(it.f, cent, it.s, 1);
		for (auto d:temp) dist[d] = min(dist[d], newdist[d]);
		temp.clear();
	}
	for (auto it:cur) dist[it] = newdist[it] = INF;
	cur.clear();
	vis[cent] = 1;
	for (auto it:adj[cent]) if (!vis[it.f]) solve(it.f);
}

int best_path(int N, int K, int H[][2], int L[]) {
	n = N, k = K;
	FOR(i, 0, n-2) {
		adj[H[i][0]].pb(pi(H[i][1], L[i]));
		adj[H[i][1]].pb(pi(H[i][0], L[i]));
	}
	FOR(i, 0, K) dist[i] = newdist[i] = INF;
	solve(0);
	return (ans == INF ? -1 : ans);
}

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