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#include<bits/stdc++.h> | |
using namespace std; | |
const int MAXN = 2500+10; | |
const int infinito = 1e9; | |
int n, m; | |
vector<int> viz[MAXN]; | |
int main() { | |
ios::sync_with_stdio(false); cin.tie(0); | |
cin >> n >> m; | |
vector<pair<int,int>> arestas; | |
for(int i = 1; i <= m; i++) { | |
int u,v; cin >> u >> v; | |
arestas.push_back(make_pair(u,v)); | |
viz[u].push_back(v); | |
viz[v].push_back(u); | |
} | |
int resposta = infinito; | |
for(int i = 0; i < m; i++) { | |
int a = arestas[i].first; | |
int b = arestas[i].second; | |
int dist[n+10]; | |
for(int j = 1; j <= n; j++) { | |
dist[j] = -1; | |
} | |
queue<int> q; | |
dist[a] = 0; | |
q.push(a); | |
// faz uma bfs partindo de a | |
while(q.size()) { | |
int u = q.front(); | |
q.pop(); | |
for(auto v : viz[u]) { | |
if((u == a && v == b) || (u == b && v == a)) continue; | |
//se for a aresta proibida nao usa | |
if(dist[v] == -1) { | |
dist[v] = dist[u]+1; | |
q.push(v); | |
} | |
} | |
} | |
if(dist[b] != -1) { | |
resposta = min(resposta, dist[b]+1); | |
} | |
} | |
if(resposta == infinito) { | |
cout << -1 << endl; | |
} | |
else { | |
cout << resposta << endl; | |
} | |
} |
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