Submission #783609

#	Time	Username	Problem	Language	Result	Execution time	Memory
783609		Magikarp4000	Highway Tolls (IOI18_highway)	C++17	51 / 100	176 ms	28716 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
#define OPTM ios_base::sync_with_stdio(0); cin.tie(0);
#define INF int(1e9+7)
#define ln '\n' 
#define ll long long
#define ull unsigned long long
#define ui unsigned int
#define us unsigned short
#define FOR(i,s,n) for (int i = s; i < n; i++)
#define FORR(i,n,s) for (int i = n; i > s; i--)
#define FORX(u, arr) for (auto u : arr)
#define PB push_back
#define in(v,x) (v.find(x) != v.end())
#define F first
#define S second
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define UM unordered_map
#define US unordered_set
#define PQ priority_queue
#define ALL(v) v.begin(), v.end()
const ll LLINF = 1e18+1;
#define int long long

struct Edge {
    int x,y,depth;
};

const int MAXN = 1.3e5+5;
int n,m;
vector<PII> v[MAXN], v1[MAXN];
vector<int32_t> w, tour;
vector<Edge> e;
int d[MAXN], ans;
bool used[MAXN];

void dfs(int s, int pa) {
    FORX(u,v1[s]) {
        if (u.F == pa) continue;
        if (e[u.S].y != u.F) swap(e[u.S].x, e[u.S].y);
        tour.PB(u.S);
        dfs(u.F,s);
    }
}

int find_edge(int s, int pa) {
    tour.clear();
    dfs(s,pa);
    // FORX(u,tour) cout << u << " ";
    // cout << ln;
    int l = -1, r = tour.size()-1;
    while (l < r) {
        FOR(i,0,m) w[i] = 0;
        int mid = (l+r+1)/2;
        FOR(i,mid,r+1) w[tour[i]] = 1;
        int val = ask(w);
        if (val == ans) r = mid-1;
        else l = mid;
    }
    // cout << "s l: " << s << " " << l << ln;
    return l == -1 ? -1 : tour[l];
}

void bfs_tree(int start, int pa) {
    FOR(i,0,n) v1[i].clear();
    queue<int> q;
    q.push(start);
    vector<bool> z(n,0);
    vector<PII> p(n,{-1,-1});
    while (!q.empty()) {
        int s = q.front();
        q.pop();
        if (z[s]) continue;
        z[s] = 1;
        FORX(u,v[s]) {
            if (!z[u.F] && u.F != pa) {
                q.push(u.F);
                p[u.F] = {s,u.S};
            }
        }
    }
    FOR(i,0,n) {
        if (p[i].F != -1) {
            v1[p[i].F].PB({i,p[i].S});
            v1[i].PB(p[i]);
            used[p[i].S] = 1;
        }
    }
}

void find_pair(int32_t N, std::vector<int32_t> U, std::vector<int32_t> V, int32_t A, int32_t B) {
    n = N; m = U.size();
    FOR(i,0,m) {
        v[U[i]].PB({V[i],i});
        v[V[i]].PB({U[i],i});
        e.PB({U[i],V[i],-1LL});
    }
    bfs_tree(0,-1);
    // FOR(i,0,n) {
    //     cout << i << ": ";
    //     FORX(u,v1[i]) cout << u.F << " ";
    //     cout << ln;
    // }
    dfs(0,-1);
    FOR(i,0,m) w.PB(0);
    ans = ask(w);
    // int l = 0, r = m-1;
    // while (l < r) {
    //     FOR(i,0,n) w[i] = 0;
    //     int mid = (l+r+1)/2;
    //     FOR(i,mid,r+1) w[tour[i]] = 1;
    //     int val = ask(w);
    //     // cout << "m a: " << mid << " " << val << ln;
    //     if (val == ans) r = mid-1;
    //     else l = mid;
    // }
    int edge = find_edge(0,-1);
    int xs = e[edge].x, ys = e[edge].y;
    // cout << "xs ys: " << xs << " " << ys << ln;
    bfs_tree(xs,ys);
    edge = find_edge(xs,ys);
    int32_t S = ys, T = edge == -1 ? xs : e[edge].y;
    // cout << "S T: " << S << " " << T << ln;
    answer(S,T);
}

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