Submission #97377

#	Time	Username	Problem	Language	Result	Execution time	Memory
97377		E869120	Highway Tolls (IOI18_highway)	C++14	90 / 100	352 ms	16708 KiB

highway

#include "highway.h"
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
using namespace std;

int N, M, U[1 << 18], V[1 << 18], dist[1 << 18], par[1 << 18], paredge[1 << 18];
vector<pair<int, int>> G[1 << 18]; bool anti[1 << 18];

void find_pair(int NN, vector<int> UU, vector<int> VV, int A, int B) {
	// ----------------------------- Step 0: Input ---------------------------
	N = NN; M = UU.size();
	for (int i = 0; i < M; i++) { U[i] = UU[i]; V[i] = VV[i]; }

	// -------------------------- Step 1: Get All-A --------------------------
	vector<int> W(M, 0);
	long long BASE = ask(W), DIST = BASE / A;

	// ---------------------- Step 2: The Minimum Vertex ---------------------
	int c1 = 0;
	for (int i = 16; i >= 0; i--) {
		for (int j = 0; j < M; j++) {
			if (min(U[j], V[j]) >= c1 + (1 << i)) W[j] = 0;
			else W[j] = 1;
		}
		long long p1 = ask(W);
		if (p1 == BASE) { c1 += (1 << i); }
	}

	// -------------------------- Step 3: Make Tree --------------------------
	for (int i = 0; i < M; i++) {
		if (min(U[i], V[i]) < c1) continue;
		G[U[i]].push_back(make_pair(V[i], i));
		G[V[i]].push_back(make_pair(U[i], i));
	}

	for (int i = 0; i < N; i++) dist[i] = (1 << 30);

	queue<int> que; que.push(c1); dist[c1] = 0;
	while (!que.empty()) {
		int pos1 = que.front(); que.pop();

		for (int i = 0; i < G[pos1].size(); i++) {
			int to = G[pos1][i].first;
			if (dist[to] > dist[pos1] + 1) {
				dist[to] = dist[pos1] + 1;
				que.push(to);
			}
		}
	}

	for (int i = c1 + 1; i < N; i++) {
		for (int j = 0; j < G[i].size(); j++) {
			int to = G[i][j].first;
			if (dist[i] > dist[to]) { par[i] = to; paredge[i] = G[i][j].second; break; }
		}
	}

	// ---------------------------- 4. Find T --------------------------------
	vector<pair<int, int>> V;
	for (int i = c1 + 1; i < N; i++) {
		if (dist[i] == (1 << 30)) continue;
		V.push_back(make_pair(dist[i], i));
	}
	sort(V.begin(), V.end());

	//for (int i = 0; i < V.size(); i++) cout << "V[" << i << "] = " << V[i].second << endl;

	int c2 = 0;
	for (int i = 16; i >= 0; i--) {
		for (int j = 0; j < W.size(); j++) W[j] = 1;
		for (int j = 0; j < c2 + (1 << i); j++) {
			if (j >= V.size()) break;
			W[paredge[V[j].second]] = 0;
		}
		long long p2 = ask(W);
		if (p2 != BASE) c2 += (1 << i);
	}

	// --------------------- 5. Find the candidate of S ----------------------
	long long T = V[c2].second, cand_dst = DIST - dist[T];
	if (cand_dst == 0) {
		answer(T, c1);
		return;
	}

	int cx = T; anti[cx] = true;
	while (true) {
		cx = par[cx];
		anti[cx] = true;
		if (cx == c1) break;
	}

	vector<int> V2;
	for (int i = c1 + 1; i < N; i++) {
		if (dist[i] == cand_dst && anti[i] == false) V2.push_back(i);
	}

	// ----------------------------- 6. Find S --------------------------------
	int c3 = 0;
	for (int i = 16; i >= 0; i--) {
		for (int j = 0; j < W.size(); j++) W[j] = 1;
		for (int j = c1 + 1; j < N; j++) W[paredge[j]] = 0;

		for (int j = 0; j < c3 + (1 << i); j++) {
			if (j >= V2.size()) break;
			W[paredge[V2[j]]] = 1;
		}
		long long p3 = ask(W);
		if (p3 == BASE) c3 += (1 << i);
	}

	long long S = V2[c3];
	answer(S, T);
	return;
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:44:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < G[pos1].size(); i++) {
                   ~~^~~~~~~~~~~~~~~~
highway.cpp:54:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < G[i].size(); j++) {
                   ~~^~~~~~~~~~~~~
highway.cpp:72:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < W.size(); j++) W[j] = 1;
                   ~~^~~~~~~~~~
highway.cpp:74:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (j >= V.size()) break;
        ~~^~~~~~~~~~~
highway.cpp:103:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < W.size(); j++) W[j] = 1;
                   ~~^~~~~~~~~~
highway.cpp:107:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (j >= V2.size()) break;
        ~~^~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 18 / 18
• Subtask 6: 21 / 31