Submission #114632

#	Time	Username	Problem	Language	Result	Execution time	Memory
114632		Shafin666	Race (IOI11_race)	C++14	0 / 100	6 ms	5120 KiB

race

#include <bits/stdc++.h>
#include "race.h"
#define mp make_pair
#define pb push_back
#define pii pair<int, int>
#define nyan "(=^･ω･^=)"
#define read_input         freopen("in.txt","r", stdin)
#define print_output       freopen("out.txt","w", stdout)
typedef long long ll;
typedef long double ld;
using namespace std;

const int maxn = 2e5+10;
const int inf = 1e6+13;

int sz[maxn], lev[maxn], dist[maxn];
int in[maxn], out[maxn], ver[maxn];
unordered_map<ll, int> M;
int idx = 1, n, k;
vector<pii> adj[maxn];

void getsz(int u, int par) {
	ver[idx] = u; in[u] = idx++;
	sz[u] = 1; lev[u] = lev[par] + 1;

	for(auto p : adj[u]) {
		int v = p.first; ll w = p.second;
		if(v == par) continue;

		dist[v] = dist[u] + w;
		getsz(v, u);
		sz[u] += sz[v];
	} out[u] = idx;
}

int ans = inf;

void dfs(int u, int par, int keep) {
	int mx = -1, bigchild = -1;

	for(auto v : adj[u]) {
		if(v.first == par) continue;
		if(sz[v.first] > mx) mx = sz[v.first], bigchild = v.first;
	}
	for(auto v : adj[u]) {
		if(v.first == par || v.first == bigchild) continue;
		dfs(v.first, u, 0);
	}

	M[dist[u]] = u;
	if(bigchild != -1) {
		dfs(bigchild, u, 1);

		ll w = k + dist[u];
		if(M.find(w) != M.end())
			ans = min(ans, lev[M[w]] - lev[u]);
	}

	for(auto v : adj[u]) {
		if(v.first == par || v.first == bigchild) continue;
		int x = v.first;
		for(int p = in[x]; p < out[x]; p++) {
			ll w = k + 2LL * dist[u] - dist[ver[p]];
			if(M.find(w) != M.end())
				ans = min(ans, lev[M[w]] + lev[ver[p]] - 2*lev[u]);
		}
		for(int p = in[x]; p < out[x]; p++) {
			int x = ver[p]; ll w = dist[x];
			if(M.find(w) == M.end() || lev[x] < lev[M[w]]) M[w] = x;
		}
	}
	if(not keep)
		M.clear();
}


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

	getsz(0, -1);
	dfs(0, -1, 0);
	if (ans == inf) return -1;
	return ans;
}

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