Submission #95411

#	Time	Username	Problem	Language	Result	Execution time	Memory
95411		popovicirobert	007 (CEOI14_007)	C++14	100 / 100	282 ms	16248 KiB

007

#include <bits/stdc++.h>
#define lsb(x) (x & (-x))
#define ll long long
#define ull unsigned long long
#define ld long double
// 217
// 44

using namespace std;

const int MAXN = (int) 2e5;

vector <int> g[MAXN + 1];
int dst[MAXN + 1][2];

inline void bfs(int nod, bool t) {
    queue <int> Q;
    dst[nod][t] = 1;
    Q.push(nod);
    while(Q.size()) {
        nod = Q.front();
        Q.pop();
        for(auto it : g[nod]) {
            if(dst[it][t] == 0) {
                dst[it][t] = dst[nod][t] + 1;
                Q.push(it);
            }
        }
    }
}

int dfs(int nod) {
    for(auto it : g[nod]) {
        if(dst[nod][0] == dst[it][0] + 1 && dst[nod][1] == dst[it][1] + 1) {
            return dfs(it) + 1;
        }
    }
    return 0;
}

int main() {
    //ifstream cin("A.in");
    //ofstream cout("A.out");
    int i, n, m, s, d, a, b;
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    cin >> n >> m;
    cin >> s >> d >> a >> b;
    for(i = 1; i <= m; i++) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    bfs(a, 0);
    bfs(b, 1);
    if(dst[s][0] - dst[d][0] != dst[s][1] - dst[d][1]) {
        cout << max(-1, min(dst[d][0] - dst[s][0], dst[d][1] - dst[s][1]));
        return 0;
    }
    int cnt_s = dfs(s), cnt_d = dfs(d);
    int ans = -1;
    if(dst[s][0] <= dst[d][0]) {
        if(cnt_s + dst[d][0] - dst[s][0] >= cnt_d) {
            ans = max(ans, dst[d][0] - dst[s][0]);
        }
        else {
            ans = max(ans, dst[d][0] - dst[s][0] - 1);
        }
    }
    cout << ans;
    //cin.close();
    //cout.close();
    return 0;
}

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