Submission #1106857

#	Time	Username	Problem	Language	Result	Execution time	Memory
1106857		thieunguyenhuy	Highway Tolls (IOI18_highway)	C++17	12 / 100	127 ms	33344 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 dep[N], e[N];
vii adj[N];
vector<int> ve[N];

#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);
		}
	}

	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

void dfs(int u, int fa) {
	for (auto [v, id] : adj[u]) if (v != fa) {
		dep[v] = dep[u] + 1, e[v] = id;
		ve[dep[v]].emplace_back(v);
		dfs(v, u);
	}
}

void find_pair(int n, vector<int> U, vector<int> V, int A, int B) {
	int m = U.size();
	for (int i = 0; i < m; ++i) {
		adj[U[i]].emplace_back(V[i], i), adj[V[i]].emplace_back(U[i], i);
	}

	dfs(0, -1);

	int low = 1, high = n - 1, depth = 0;
	while (low <= high) {
		int mid = low + high >> 1; vector<int> w(m, HEAVY); ll expected = 1ll * mid * A;
		for (int d = 1; d <= mid; ++d) for (auto v : ve[d]) {
			w[e[v]] = LIGHT;
		}
		// cerr << mid << ' ' << ask(w) << '\n';
		if (expected <= ask(w)) low = (depth = mid) + 1;
		else high = mid - 1;
	}

	cerr << "depth = " << depth << '\n';
	for (auto &x : ve[depth]) cerr << x << ' ';
	cerr << '\n';

	low = 0, high = ve[depth].size() - 1; int pos = -1; ll expected = 1ll * depth * B;
	while (low <= high) {
		int mid = low + high >> 1; vector<int> w(m, HEAVY);
		for (int i = 0; i <= mid; ++i) w[e[ve[depth][i]]] = LIGHT;
		// cerr << mid << ' ' << ask(w) << '\n';
		if (ask(w) < expected) high = (pos = mid) - 1;
		else low = mid + 1;
	}

	answer(0, ve[depth][pos]);
}

#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();
    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:140:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  140 |   int mid = low + high >> 1; vector<int> w(m, HEAVY); ll expected = 1ll * mid * A;
      |             ~~~~^~~~~~
highway.cpp:155:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  155 |   int mid = low + high >> 1; vector<int> w(m, HEAVY);
      |             ~~~~^~~~~~

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