Submission #167156

#	Time	Username	Problem	Language	Result	Execution time	Memory
167156		Lightning	Evacuation plan (IZhO18_plan)	C++17	0 / 100	4019 ms	14604 KiB

plan

#include <iostream>
#include <algorithm>
#include <vector>
#include <set>

using namespace std;

typedef pair <int, int> pii;

#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define pb push_back
#define mkp make_pair
#define F first
#define S second

const int N = 1e5 + 5;
const int INF = 1e9 + 5;

int n, m, k, q;
vector <pii> g[N];
vector <int> new_gr[N];
set <pii> st;
int dist[N], up[N][18], pr[N], tin[N], tout[N], tiktak;
bool was[N];

void dijkstra() {
	while(sz(st)) {
		int v = st.begin() -> S;
		st.erase(st.begin());
		for(pii it : g[v]) {
			int w = it.F;
			int to = it.S;
			if(dist[to] > dist[v] + w) {
				st.erase(mkp(dist[to], to));
				dist[to] = dist[v] + w;
				st.insert(mkp(dist[to], to));
			} 
		}
	}
}

int get_par(int v) {
	if(pr[v] == v) return v;
	return get_par(pr[v]);
}

void dfs(int v, int pre) {
	tin[v] = ++tiktak;
	up[v][0] = pre;
	for(int i = 1; i <= 17; ++i) {
		up[v][i] = up[up[v][i - 1]][i - 1];
	}
	for(int to : new_gr[v]) {
		if(to != pre) 
			dfs(to, v);
	}
	tout[v] = ++tiktak;
}

bool upper(int a, int b) {
	return (tin[a] <= tin[b] && tout[b] <= tout[a]);
}

int lca(int a, int b) {
	if(upper(a, b)) return a;
	if(upper(b, a)) return b;
	for(int i = 17; i >= 0; --i) {
		if(!upper(up[a][i], b)) {
			a = up[a][i];
			break;
		}
	}
	return up[a][0];
}

int main () {
//	ios_base::sync_with_stdio(false);
//	cin.tie(NULL);
	scanf("%d%d", &n, &m);		
	for(int i = 1; i <= m; ++i) {
		int a, b, c;
		scanf("%d%d%d", &a, &b, &c);		
		g[a].pb(mkp(c, b));
		g[b].pb(mkp(c, a));
	}
	for(int i = 1; i <= n; ++i) 
		dist[i] = INF, pr[i] = i;
	scanf("%d", &k);
	for(int i = 1; i <= k; ++i) {
		int b; scanf("%d", &b);
		dist[b] = 0;
		st.insert(mkp(0, b));
	}
	dijkstra();
	vector <pii> vec;
	for(int i = 1; i <= n; ++i) {
		vec.pb(mkp(dist[i], i));
	}
	sort(all(vec));
	for(int i = sz(vec) -1 ; i >= 0; --i) {
		int v = vec[i].S;
		was[v] = 1;
		for(pii it : g[v]) {
			int to = it.S;
			int par_to = get_par(to);
			if(was[to] && v != par_to) {
				pr[par_to] = v;
//				show(v);
//				show(to);
//				cerr << '\n';
				new_gr[v].pb(par_to);
				new_gr[par_to].pb(v);
			}
		}
	}
	// lca preprocess
	dfs(vec[n - 1].S, vec[n - 1].S);
	scanf("%d", &q);
	for(int it = 1; it <= q; ++it) {
		int s, t; scanf("%d%d", &s, &t);
		printf("%d\n", dist[lca(s, t)]);
	}
	return 0;
}
/*
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
*/

Compilation message (stderr)

plan.cpp: In function 'int main()':
plan.cpp:80:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);  
  ~~~~~^~~~~~~~~~~~~~~~
plan.cpp:83:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d", &a, &b, &c);  
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~
plan.cpp:89:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &k);
  ~~~~~^~~~~~~~~~
plan.cpp:91:15: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int b; scanf("%d", &b);
          ~~~~~^~~~~~~~~~
plan.cpp:119:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &q);
  ~~~~~^~~~~~~~~~
plan.cpp:121:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int s, t; scanf("%d%d", &s, &t);
             ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 13
• Subtask 3: 0 / 12
• Subtask 4: 0 / 19
• Subtask 5: 0 / 46