Submission #122901

#	Time	Username	Problem	Language	Result	Execution time	Memory
122901		eriksuenderhauf	Highway Tolls (IOI18_highway)	C++11	51 / 100	265 ms	10236 KiB

highway

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include "highway.h"
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
#define mem(a,v) memset((a), (v), sizeof (a))
#define enl printf("\n")
#define case(t) printf("Case #%d: ", (t))
#define ni(n) scanf("%d", &(n))
#define nl(n) scanf("%I64d", &(n))
#define nai(a, n) for (int i = 0; i < (n); i++) ni(a[i])
#define nal(a, n) for (int i = 0; i < (n); i++) nl(a[i])
#define pri(n) printf("%d\n", (n))
#define prl(n) printf("%I64d\n", (n))
#define pii pair<int, int>
#define pil pair<int, long long>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vil vector<pil>
#define vll vector<pll>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<int,int,hash<int>> ht;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> oset;
const double pi = acos(-1);
const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;
const int MAXN = 90050;
const double eps = 1e-9;
vii adj[MAXN], all;
int n, vis[MAXN], dp[MAXN];
ll dist;

int solve(int root) {
	mem(vis, 0);
	mem(dp, 0);
	deque<int> pq;
	pq.pb(root);
	vi edg;
	while (!pq.empty()) {
		int u = pq.front(); pq.pop_front();
		vis[u] = 1;
		for (pii nx: adj[u]) {
			if (vis[nx.fi]) continue;
			dp[nx.fi] = dp[u] + 1;
			pq.pb(nx.fi);
			edg.pb(nx.se);
		}
	}
	reverse(edg.begin(), edg.end());
	//for (int i = 0; i < edg.size(); i++) {
		//cerr << edg[i] << " " << all[edg[i]].fi << " " << all[edg[i]].se << "\n";
	//}
	int lo = 0, hi = n-1, ans = 0;
	while (lo <= hi) {
		int mi = (lo+hi) / 2;
		vi tmp(n-1);
		for (int i = 0; i <= mi; i++)
			tmp[edg[i]] = 1;
		ll w = ask(tmp);
		//cerr << "ask: " << w << ": ";
		for (int i = 0; i < tmp.size(); i++)
			//cerr << tmp[i] << " ";
		//cerr << "\n";
		if (w == dist)
			lo = mi + 1;
		else
			hi = mi - 1;
	}
	pii ret = all[edg[lo]];
	//cerr << ret.fi << " " << ret.se << "\n";
	if (dp[ret.fi] < dp[ret.se])
		swap(ret.fi, ret.se);
	return ret.fi;
}

void find_pair(int N, vi U, vi V, int a, int b) {
	n = N;
	for (int i = 0; i+1 < n; i++) {
		adj[U[i]].pb(mp(V[i],i));
		adj[V[i]].pb(mp(U[i],i));
		all.pb(mp(U[i], V[i]));
	}
	dist = ask(vi(n-1, 0));
	int s = solve(0);
	int t = solve(s);
	//cerr << s << " " << t << "\n";
	answer(s, t);
}

/*int main() {

    return 0;
}*/

Compilation message (stderr)

highway.cpp: In function 'int solve(int)':
highway.cpp:70:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < tmp.size(); i++)
                   ~~^~~~~~~~~~~~
highway.cpp:62:24: warning: unused variable 'ans' [-Wunused-variable]
  int lo = 0, hi = n-1, ans = 0;
                        ^~~

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