Submission #379026

#	Time	Username	Problem	Language	Result	Execution time	Memory
379026		rk42745417	Evacuation plan (IZhO18_plan)	C++17	100 / 100	620 ms	41036 KiB

plan

#include <bits/stdc++.h>
using namespace std;

using ll = int64_t;
using ull = uint64_t;
using uint = uint32_t;
using ld = long double;
const int MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const ll LINF = 2e18;
const double EPS = 1e-9;
#define EMT ios::sync_with_stdio(0); cin.tie(0);

const int N = 1e5 + 25, LGN = 18;
int dis[N], anc[LGN][N], dep[N], mn[LGN][N];
bool vis[N];
vector<int> npp;
vector<pair<int, int>> edge[N];
vector<int> nwedge[N];

struct DisjointSet {
	int pa[N], sz[N];
	void init(int n) {
		for(int i = 1; i <= n; i++)
			sz[i] = 1, pa[i] = i;
	}
	int fnd(int x) { return pa[x] == x ? pa[x] : fnd(pa[x]); }
	bool uni(int a, int b) {
		if((a = fnd(a)) == (b = fnd(b)))
			return false;
		if(sz[a] > sz[b])
			swap(a, b);
		sz[b] += sz[a];
		pa[a] = b;
		return true;
	}
} dsu;
void solve() {
	memset(dis, 0x3f, sizeof dis);
	priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
	for(int a : npp)
		dis[a] = 0, pq.push({dis[a], a});
	while(!pq.empty()) {
		auto [c, u] = pq.top();
		pq.pop();
		if(c > dis[u])
			continue;
		for(const auto &[v, d] : edge[u]) {
			if(dis[v] > c + d) {
				dis[v] = c + d;
				pq.push({dis[v], v});
			}
		}
	}
};
void dfs(int u, int p) {
	for(int v : nwedge[u]) {
		if(v == p)
			continue;
		dep[v] = dep[u] + 1;
		mn[0][v] = dis[v];
		anc[0][v] = u;
		dfs(v, u);
	}
}
void build(int n) {
	for(int i = 1; i < LGN; i++)
		for(int j = 1; j <= n; j++)
			anc[i][j] = anc[i - 1][anc[i - 1][j]], mn[i][j] = min(mn[i - 1][j], mn[i - 1][anc[i - 1][j]]);
}
int lca(int a, int b) {
	int res = INF;
	if(dep[a] < dep[b])
		swap(a, b);
	for(int i = 0, x = dep[a] - dep[b]; i < LGN; i++)
		if(x >> i & 1)
			res = min(res, mn[i][a]), a = anc[i][a];
	if(a == b)
		return min(res, dis[a]);
	for(int i = LGN - 1; ~i; i--) {
		if(anc[i][a] == anc[i][b])
			continue;
		res = min(res, mn[i][a]);
		res = min(res, mn[i][b]);
		a = anc[i][a];
		b = anc[i][b];
	}
	return min({res, mn[0][a], mn[0][b], dis[anc[0][a]]});
}
const int SQN = 350;
signed main() { EMT
	int n, m;
	cin >> n >> m;
	for(int i = 0; i < m; i++) {
		int u, v, w;
		cin >> u >> v >> w;
		edge[u].push_back({v, w});
		edge[v].push_back({u, w});
	}

	int k;
	cin >> k;
	npp.resize(k);
	for(int &a : npp)
		cin >> a;
	
	solve();
	dsu.init(n);
	vector<pair<int, int>> tmp(n);
	for(int i = 1; i <= n; i++) {
		tmp[i - 1] = {dis[i], i};
	}
	sort(tmp.begin(), tmp.end(), greater<pair<int, int>>());

	for(const auto &[w, u] : tmp) {
		vis[u] = 1;
		for(const auto &[v, d] : edge[u])
			if(vis[v] && dsu.uni(u, v))
				nwedge[u].push_back(v), nwedge[v].push_back(u);
	}
	assert(dsu.sz[dsu.fnd(1)] == n);
	dfs(1, 1);
	build(n);
	int q;
	cin >> q;
	while(q--) {
		int a, b;
		cin >> a >> b;
		cout << lca(a, b) << '\n';
	}
}
/*
9 12
1 9 4
1 2 5
2 3 7
2 4 3
4 3 6
3 6 4
8 7 10
6 7 5
5 8 1
9 5 7
5 4 12
6 8 2
2
4 7
5
1 6
5 3
4 8
5 8
1 5

*/

• Subtask 1: 10 / 10
• Subtask 2: 13 / 13
• Subtask 3: 12 / 12
• Subtask 4: 19 / 19
• Subtask 5: 46 / 46