Submission #1106990

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106990		thieunguyenhuy	Highway Tolls (IOI18_highway)	C++17	51 / 100	178 ms	32104 KiB

highway

#ifndef hwe
	#include "highway.h"
#endif
 
#include <bits/stdc++.h>
using namespace std;
 
#define popcount(n) (__builtin_popcountll((n)))
#define clz(n) (__builtin_clzll((n)))
#define ctz(n) (__builtin_ctzll((n)))
#define lg(n) (63 - __builtin_clzll((n)))
#define BIT(n, i) (((n) >> (i)) & 1ll)
#define MASK(i) (1ll << (i))
#define FLIP(n, i) ((n) ^ (1ll << (i)))
#define ON(n, i) ((n) | MASK(i))
#define OFF(n, i) ((n) & ~MASK(i))
 
#define Int __int128
#define fi first
#define se second
 
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef pair<long long, int> pli;
typedef pair<int, long long> pil;
typedef vector<pair<int, int>> vii;
typedef vector<pair<long long, long long>> vll;
typedef vector<pair<long long, int>> vli;
typedef vector<pair<int, long long>> vil;
 
template <class T1, class T2>
bool maximize(T1 &x, T2 y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}
template <class T1, class T2>
bool minimize(T1 &x, T2 y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
 
template <class T>
void remove_duplicate(vector<T> &ve) {
    sort (ve.begin(), ve.end());
    ve.resize(unique(ve.begin(), ve.end()) - ve.begin());
}
 
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
template <class T> T random(T l, T r) {
    return uniform_int_distribution<T>(l, r)(rng);
}
template <class T> T random(T r) {
    return rng() % r;
}
 
const int N = 90000 + 5;
const int MOD = 1e9 + 7;
const int inf = 1e9;
const ll INF = 1e18;
 
const int LIGHT = 0, HEAVY = 1;
 
int asked = 0, maxDepth, dep[N], e[N];
vii adj[N];
vector<int> ve[N];
map<vector<int>, ll> mem;
 
#ifdef hwe
namespace Grader {
	int n, m, s, t;
	ll dist[N];
	pii edges[N];
	vii adj[N];
	vector<int> w;
 
	void get() {
		cin >> n >> m >> s >> t;
	
		for (int i = 0; i < m; ++i) {
			int u, v; cin >> u >> v;
			adj[u].emplace_back(v, i), adj[v].emplace_back(u, i);
			edges[i] = make_pair(u, v);
		}
	}

	void rand() {
		n = random(7, 10), m = random(n - 1, 20), s = random(n), t = random(n);
		while (s == t) t = random(n);
		for (int i = 1; i < n; ++i) {
			edges[i - 1] = make_pair(random(i), i);
		}
		for (int i = n - 1; i < m; ++i) {
			edges[i] = make_pair(random(i), random(i));
		}
		for (int i = 0; i < m; ++i) {
			int u, v; tie(u, v) = edges[i];
			adj[u].emplace_back(v, i), adj[v].emplace_back(u, i);
		}
	}

	void show() {
		cerr << n << ' ' << m << ' ' << s << ' ' << t << '\n';
		for (int i = 0; i < m; ++i) cerr << edges[i].fi << ' ' << edges[i].se << '\n';
	}
 
	ll dijkstra(int s, int t) {
		memset(dist, 0x0f, sizeof dist); dist[s] = 0;
		priority_queue<pli, vli, greater<pli>> pq; pq.emplace(0, s);
		while (!pq.empty()) {
			int u = pq.top().se; pq.pop();
			// cerr << "dijkstra " << u << ' ' << dist[u] << '\n';
			for (auto [v, id] : adj[u]) if (minimize(dist[v], dist[u] + w[id])) {
				pq.emplace(dist[v], v);
			}
		}
		return dist[t];
	}
 
	ll ask(const vector<int> &_w) {
		w = _w; for (auto &x : w) ++x;
		return dijkstra(s, t);
	}
}
 
ll ask(const vector<int> &w) {
	return Grader::ask(w);
}
 
void answer(int s, int t) {
	cerr << "Answer " << s << ' ' << t << '\n';
}
#endif
 
ll myask(const vector<int> &w) {
	auto it = mem.find(w);
	if (it != mem.end()) return it->se;
	assert(++asked <= 50);
	return mem[w] = ask(w);
}
 
void bfs(int root) {
	memset(dep, -1, sizeof dep); dep[root] = maxDepth = 0;
	queue<int> q; q.emplace(root);
	while (!q.empty()) {
		int u = q.front(); q.pop();
		maximize(maxDepth, dep[u]);
		for (auto [v, id] : adj[u]) if (dep[v] == -1) {
			dep[v] = dep[u] + 1;
			q.emplace(v);
		}
	}
}
 
void find_pair(int n, vector<int> U, vector<int> V, int A, int B) {
	int m = U.size(); asked = 0;
	for (int i = 0; i < m; ++i) {
		adj[U[i]].emplace_back(V[i], i), adj[V[i]].emplace_back(U[i], i);
	}
 
	vector<int> w(m, LIGHT);
	ll fixed = myask(w); int numEdges = fixed / A, depthS = numEdges;
	cerr << "numEdges = " << numEdges << '\n';

	bfs(0); for (int i = 1; i < n; ++i) ve[i].clear();
	for (int i = 0; i < m; ++i) {
		int u = U[i], v = V[i];
		if (dep[u] >= dep[v]) ve[dep[u]].emplace_back(i);
		if (dep[v] >= dep[u]) ve[dep[v]].emplace_back(i);
	}

	// cerr << "depth: ";
	// for (int i = 0; i < n; ++i) cerr << dep[i] << ' ';
	// cerr << '\n';

	auto check = [&](int mid) {
		vector<int> w(m, HEAVY);
		for (int d = 1; d <= mid; ++d) for (auto id : ve[d]) {
			w[id] = LIGHT;
		}
		return myask(w) == fixed;
	};
 
	int low = 1, high = maxDepth, depthT = 0;
	while (low <= high) {
		int mid = low + high >> 1;
		if (check(mid)) high = (depthT = mid) - 1;
		else low = mid + 1;
	}

	// cerr << "kq ";
	// for (auto &x : ve[3]) cerr << x << ' ';
	// cerr << '\n';
	// cerr << "check = " << check(3) << '\n';
 	// cerr << "depthT = " << depthT << '\n';

 	assert(!ve[depthT].empty());
	low = 0, high = int(ve[depthT].size()) - 2; int posT = ve[depthT].size() - 1;
	while (low <= high) {
		int mid = low + high >> 1; vector<int> w(m, HEAVY);
		for (int i = 0; i <= mid; ++i) w[ve[depthT][i]] = LIGHT;
		if (myask(w) < 1ll * numEdges * B) high = (posT = mid) - 1;
		else low = mid + 1;
	}
	int idT = ve[depthT][posT], T = (dep[U[idT]] + 1 == dep[V[idT]] ? V[idT] : U[idT]);
	cerr << "T = " << T << '\n';

	bfs(T); for (int i = 1; i < n; ++i) ve[i].clear();
	for (int i = 0; i < m; ++i) {
		int u = U[i], v = V[i];
		if (dep[u] >= dep[v]) ve[dep[u]].emplace_back(i);
		if (dep[v] >= dep[u]) ve[dep[v]].emplace_back(i);
	}
 
 	assert(!ve[depthS].empty());
	low = 0, high = int(ve[depthS].size()) - 2; int posS = ve[depthS].size() - 1;
	while (low <= high) {
		int mid = low + high >> 1; vector<int> w(m, HEAVY);
		for (int i = 0; i <= mid; ++i) w[ve[depthS][i]] = LIGHT;
		// cerr << mid << ' ' << myask(w) << '\n';
		if (myask(w) < 1ll * numEdges * B) high = (posS = mid) - 1;
		else low = mid + 1;
	}
	int idS = ve[depthS][posS], S = (dep[U[idS]] + 1 == dep[V[idS]] ? V[idS] : U[idS]);
 
	answer(S, T);
}
 
#ifdef hwe
signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
 
    #ifdef hwe
        freopen("input.inp", "r", stdin);
        freopen("output.out", "w", stdout);
    #else
        #define taskname ""
        if (fopen(taskname".inp", "r")) {
            freopen(taskname".inp", "r", stdin);
            freopen(taskname".out", "w", stdout);
        }
    #endif
 
    Grader::get(); Grader::show();
    int n = Grader::n; vector<int> U, V;
    for (int i = 0; i < Grader::m; ++i) {
    	int u, v; tie(u, v) = Grader::edges[i];
    	U.emplace_back(u), V.emplace_back(v);
    }
    find_pair(n, U, V, 1, 2);
 
    cerr << '\n'; return 0;
}
#endif

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:194:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  194 |   int mid = low + high >> 1;
      |             ~~~~^~~~~~
highway.cpp:208:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  208 |   int mid = low + high >> 1; vector<int> w(m, HEAVY);
      |             ~~~~^~~~~~
highway.cpp:226:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  226 |   int mid = low + high >> 1; vector<int> w(m, HEAVY);
      |             ~~~~^~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31