Submission #155941

#	Time	Username	Problem	Language	Result	Execution time	Memory
155941		Akashi	007 (CEOI14_007)	C++14	100 / 100	437 ms	18016 KiB

007

#include <bits/stdc++.h>
using namespace std;
 
int n, m;
bool viz[200005];
int s, d, a, b;
int da[200005], db[200005], ds[200005], dd[200005];
queue <int> q;
vector <int> v[200005];
 
void bfs(int nod, int d[]){
    for(int i = 1; i <= n ; ++i) d[i] = 1e9;
    memset(viz, 0, sizeof(viz));
 
    q.push(nod);
    d[nod] = 0; viz[nod] = 1;
    while(!q.empty()){
        int nod = q.front();
        q.pop();
 
        for(auto it : v[nod]){
            if(viz[it]) continue ;
            q.push(it);
            viz[it] = 1;
            d[it] = d[nod] + 1;
        }
    }
}
 
int main()
{
//    freopen("1.in", "r", stdin);
    scanf("%d%d", &n, &m);
    scanf("%d%d%d%d", &s, &d, &a, &b);
 
    int x, y;
    for(int i = 1; i <= m ; ++i){
        scanf("%d%d", &x, &y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
 
    bfs(a, da);
    bfs(b, db);
    bfs(s, ds);
    bfs(d, dd);
 
    if(dd[b] < ds[b] || dd[a] < ds[a]){
        printf("-1");
        return 0;
    }
 
    int tmp = -1;
    if(dd[b] - ds[b] != dd[a] - ds[a])
        tmp = min(dd[b] - ds[b], dd[a] - ds[a]);
    else{
        int dif = min(dd[b] - ds[b], dd[a] - ds[a]), nr1 = 0, nr2 = 0;
        for(int i = 1; i <= n ; ++i)
            if(da[i] == db[i] && da[i] + ds[i] == ds[a]) nr1 = max(nr1, ds[i]);
 
        for(int i = 1; i <= n ; ++i)
            if(da[i] == db[i] && da[i] + dd[i] == dd[a]) nr2 = max(nr2, dd[i]);
 
        if(nr1 >= nr2 - dif) tmp = min(dd[b] - ds[b], dd[a] - ds[a]);
        else tmp = min(dd[b] - ds[b], dd[a] - ds[a]) - 1;
    }
 
    printf("%d", tmp);
 
    return 0;
}
 

Compilation message (stderr)

007.cpp: In function 'int main()':
007.cpp:33:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~
007.cpp:34:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d", &s, &d, &a, &b);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
007.cpp:38:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &x, &y);
         ~~~~~^~~~~~~~~~~~~~~~

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