Submission #257840

#	Time	Username	Problem	Language	Result	Execution time	Memory
257840		doowey	007 (CEOI14_007)	C++14	100 / 100	371 ms	18132 KiB

007

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

#define fi first
#define se second
#define mp make_pair
#define fastIO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

const int N = (int)2e5 + 10;
vector<int> T[N];

int c = 0;
int d[4][N];
int n;

void bfs(int node){
    for(int i = 1; i <= n; i ++ )
        d[c][i] = (int)1e9;
    queue<int> bf;
    bf.push(node);
    d[c][node] = 0;
    while(!bf.empty()){
        node = bf.front();
        bf.pop();
        for(auto x : T[node]){
            if(d[c][x] > d[c][node] + 1){
                d[c][x] = d[c][node] + 1;
                bf.push(x);
            }
        }
    }
    c ++ ;
}

int main(){
    fastIO;
    int m;
    cin >> n >> m;
    int a, b;
    cin >> a >> b;
    int n0, n1;
    cin >> n0 >> n1;
    int u, v;
    for(int i = 0 ; i < m ; i ++ ){
        cin >> u >> v;
        T[u].push_back(v);
        T[v].push_back(u);
    }
    bfs(a);
    bfs(b);
    bfs(n0);
    bfs(n1);
    int d0 = d[1][n0] - d[0][n0];
    int d1 = d[1][n1] - d[0][n1];
    if(d0 != d1){
        int low = min(d0,d1);
        if(low < 0) cout << -1 << "\n";
        else cout << low << "\n";
        return 0;
    }

    int cc = 0, dd = 0;
    for(int i = 1; i <= n; i ++ ){
        if(d[0][i] + d[2][i] == d[0][n0] && d[0][i] + d[3][i] == d[0][n1]){
            cc = max(cc, d[0][i]);
        }
        if(d[1][i] + d[2][i] == d[1][n0] && d[1][i] + d[3][i] == d[1][n1]){
            dd = max(dd, d[1][i]);
        }
    }
    if(d0 < 0){
        cout << -1 << "\n";
        return 0;
    }
    if(cc + d0 >= dd){
        cout << d0 << "\n";
        return 0;
    }
    cout << d0-1 << "\n";
    return 0;
}

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