Submission #65177

#	Time	Username	Problem	Language	Result	Execution time	Memory
65177		kingpig9	Evacuation plan (IZhO18_plan)	C++11	100 / 100	1483 ms	20992 KiB

plan

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int MAXN = 1e5 + 10, INF = 1e8;

#define debug(...) fprintf(stderr, __VA_ARGS__)
#define all(v) (v).begin(), (v).end()
#define fi first
#define se second
#define fillchar(a, s) memset((a), (s), sizeof(a))

int N, M;
vector<pii> adj[MAXN];

struct union_find {
	int par[MAXN];

	void reset() {
		for (int i = 0; i < N; i++) {
			par[i] = i;
		}
	}

	int find (int x) {
		return x == par[x] ? x : par[x] = find(par[x]);
	}

	void merge (int x, int y) {
		par[find(x)] = find(y);
	}
} uf;

int K, G[MAXN];
int dist[MAXN];
bool vis[MAXN];
int dord[MAXN];	//order of dist

int Q;
int S[MAXN], T[MAXN];
int ind[MAXN], lo[MAXN], hi[MAXN], mid[MAXN];

//code for dijkstra
void dijkstra() {
	priority_queue<pii, vector<pii>, greater<pii>> pq;
	for (int i = 0; i < N; i++) {
		dist[i] = INF;
	}

	for (int i = 0; i < K; i++) {
		int x = G[i];
		dist[x] = 0;
		pq.push({0, x});
	}

	while (!pq.empty()) {
		int u = pq.top().se, w = pq.top().fi;
		pq.pop();
		if (vis[u]) {
			continue;
		}

		vis[u] = true;
		for (pii e : adj[u]) {
			int v = e.se;
			int nw = e.fi + w;

			if (dist[v] > nw) {
				dist[v] = nw;
				pq.push({nw, v});
			}
		}
	}

	/*
	for (int i = 0; i < N; i++) {
		debug("dist[%d] = %d\n", i, dist[i]);
	}
	*/
}

bool cmpd (int x, int y) {
	return dist[x] > dist[y];
}

bool cmp (int x, int y) {
	return mid[x] > mid[y];
}

int main() {
	scanf("%d %d", &N, &M);
	for (int i = 0; i < M; i++) {
		int a, b, w;
		scanf("%d %d %d", &a, &b, &w);
		a--;
		b--;
		adj[a].push_back({w, b});
		adj[b].push_back({w, a});
	}

	scanf("%d", &K);
	for (int i = 0; i < K; i++) {
		scanf("%d", &G[i]);
		G[i]--;
	}

	dijkstra();

	scanf("%d", &Q);
	for (int i = 0; i < Q; i++) {
		scanf("%d %d", &S[i], &T[i]);
		S[i]--;
		T[i]--;
		lo[i] = 0;	//ans always >= lo[i], always < hi[i]
		hi[i] = INF;
	}

	iota(dord, dord + N, 0);
	sort(dord, dord + N, cmpd);

	//code for parallel bsearch
	for (int iter = 0; iter < 28; iter++) {
		for (int i = 0; i < Q; i++) {
			mid[i] = (lo[i] + hi[i]) / 2;
			ind[i] = i;
		}
		sort(ind, ind + Q, cmp);
		uf.reset();

		int dptr = 0;
		for (int ii = 0; ii < Q; ii++) {
			int i = ind[ii];
			for (; dptr < N && dist[dord[dptr]] >= mid[i]; dptr++) {
				//try to merge if you can
				int x = dord[dptr];
				for (pii e : adj[x]) {
					int y = e.se;
					if (dist[y] >= mid[i]) {
						uf.merge(x, y);
					}
				}
			}

			if (uf.find(S[i]) == uf.find(T[i])) {
				lo[i] = mid[i];
			} else {
				hi[i] = mid[i];
			}
		}
	}

	//code for final output
	for (int i = 0; i < Q; i++) {
		printf("%d\n", lo[i]);
	}
}

Compilation message (stderr)

plan.cpp: In function 'int main()':
plan.cpp:92:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &N, &M);
  ~~~~~^~~~~~~~~~~~~~~~~
plan.cpp:95:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d %d", &a, &b, &w);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
plan.cpp:102:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &K);
  ~~~~~^~~~~~~~~~
plan.cpp:104:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &G[i]);
   ~~~~~^~~~~~~~~~~~~
plan.cpp:110:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &Q);
  ~~~~~^~~~~~~~~~
plan.cpp:112:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &S[i], &T[i]);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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