Submission #793361

#	Time	Username	Problem	Language	Result	Execution time	Memory
793361		Valaki2	007 (CEOI14_007)	C++14	10 / 100	224 ms	17740 KiB

007

#include <bits/stdc++.h>
using namespace std;

#define pb push_back

const int maxn = 2e5;

int n, m;
vector<int> graph[1 + maxn];
int g, s, a, b;
vector<int> dg, ds, da, db;

vector<int> bfs(int start) {
    vector<int> res(1 + n, -1);
    res[start] = 0;
    queue<int> q;
    q.push(start);
    while(!q.empty()) {
        int cur = q.front();
        q.pop();
        for(int nei : graph[cur]) {
            if(res[nei] == -1) {
                res[nei] = res[cur] + 1;
                q.push(nei);
            }
        }
    }
    return res;
}

void solve() {
    cin >> n >> m;
    cin >> g >> s >> a >> b;
    for(int i = 0; i < m; i++) {
        int x, y;
        cin >> x >> y;
        graph[x].pb(y);
        graph[y].pb(x);
    }
    dg = bfs(g), ds = bfs(s), da = bfs(a), db = bfs(b);
    if((da[s] < da[g]) || (db[s] < db[g])) {
        cout << "-1\n";
        return;
    }
    int add_a = da[s] - 1 - da[g], add_b = db[s] - 1 - db[g];
    bool extra_case = true;
    if(add_a != add_b) {
        add_a++, add_b++;
        extra_case = false;
    }
    int to_add = min(add_a, add_b);
    if(!extra_case) {
        cout << to_add << "\n";
        return;
    }
    to_add++;
    da[s] += to_add;
    db[s] += to_add;
    int closest_g = n + 1, closest_s = n + 1;
    if(da[s] != db[s] || da[g] != db[g]) {
        exit(1);
    }
    for(int cur = 1; cur <= n; cur++) {
        /*int max_dab = max(da[cur], db[cur]), min_dab = min(da[cur], db[cur]);
        if((max_dab + closest_g == max(da[g], db[g])) && (min_dab + closest_g == min(da[g], db[g]))) {
            closest_g = min(closest_g, max_dab);
        }
        if((max_dab + closest_s == max(da[s], db[s]))) {
            closest_s = min(closest_s, max_dab);
        }*/
        int dab = max(da[cur], db[cur]);
        if(dab + dg[cur] == max(da[g], db[g])) {
            closest_g = min(closest_g, dab);
        }
        if(dab + dg[cur] == max(da[s], db[s])) {
            closest_s = min(closest_s, dab);
        }
    }
    if(closest_s < closest_g) {
        to_add--;
    }
    cout << to_add << "\n";
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

• Subtask 1: 3 / 30
• Subtask 2: 7 / 70