Submission #415382

#	Time	Username	Problem	Language	Result	Execution time	Memory
415382		Kevin_Zhang_TW	Highway Tolls (IOI18_highway)	C++17	0 / 100	31 ms	14972 KiB

highway

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV 
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif

const int MAX_N = 300010;
#include "highway.h"

int n, m, dis;
vector<int> edge[MAX_N];
vector<pair<int,int>> alle;
ll A, B;

ll qry(vector<int> ban_list) {
	debug(AI(ban_list));
	vector<int> ban(n);
	for (int u : ban_list) ban[u] = true;
	vector<int> w(m);
	for (int i = 0;i < m;++i) {
		auto [x, y] = alle[i];
		w[i] = ban[x] || ban[y];
	}
	return ask(w);
}

void solve_tree_rt(int rt) {

	vector<int> stk;
	function<void(int,int)> dfs = [&](int x, int lst) {
		stk.pb(x);
		for (int u : edge[x]) if (u != lst)
			dfs(u, x);
	};
	dfs(rt, rt);

	int l = 0, r = n-1, mid;
	while (l < r) {
		mid = l + r >> 1;
		ll v = qry( vector<int>(begin(stk), begin(stk)+mid ) );

		ll more = (v - dis * A) / (B-A);
		if (more < dis)
			l = mid+1;
		else
			r = mid;
	}

	answer(rt, stk[l]);
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
	::A = A, ::B = B;
	n = N, m = U.size();

	assert(m == n-1);

	for (int i = 0;i < m;++i) {
		alle.pb(U[i], V[i]);
		edge[U[i]].pb(V[i]);
		edge[V[i]].pb(U[i]);
	}

	dis = qry( {} ) / A;

	solve_tree_rt(0);

}

Compilation message (stderr)

highway.cpp: In function 'll qry(std::vector<int>)':
highway.cpp:15:20: warning: statement has no effect [-Wunused-value]
   15 | #define debug(...) 0
      |                    ^
highway.cpp:27:2: note: in expansion of macro 'debug'
   27 |  debug(AI(ban_list));
      |  ^~~~~
highway.cpp: In function 'void solve_tree_rt(int)':
highway.cpp:50:11: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   50 |   mid = l + r >> 1;
      |         ~~^~~

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