#include <bits/stdc++.h>
#define err(args...) {}
#ifdef DEBUG
#include "_debug.cpp"
#endif
using namespace std;
using ll = long long;
using ld = long double;
template <typename T> using lim = numeric_limits<T>;
template <typename T> istream& operator>>(istream& is, vector<T>& a) { for(T& x : a) { is >> x; } return is; }
template <typename X, typename Y> istream& operator>>(istream& is, pair<X, Y>& p) { return is >> p.first >> p.second; }
struct edge {
int u, v;
edge reverse() const { return {v, u}; }
friend ostream& operator<<(ostream& os, const edge& e) {
return os << "{u: " << e.u << ", v: " << e.v << "}";
}
};
template <bool Directed, typename TEdge, bool Index> struct graph {
using EType = TEdge;
vector<TEdge> edges;
vector<vector<int>> adj;
graph(int n) : adj(n + Index) {}
graph(int n, int m) : graph(n) { edges.reserve(m << not Directed); }
TEdge& operator()(int e) { return edges[e]; }
vector<int>& operator[](int u) { return adj[u]; }
int size() { return adj.size() - Index; }
void append(int u, const TEdge& e) {
adj[u].push_back(edges.size());
edges.push_back(e);
}
void add_edge(const TEdge& e) {
append(e.u, e);
if(not Directed) append(e.v, e.reverse());
}
};
template <typename TEdge, bool Index> pair<vector<int>, vector<vector<int>>> find_2eccs(graph<0, TEdge, Index>& g) {
vector<int> vis(g.adj.size()), low(g.adj.size()), cut_edge(g.edges.size()), s;
vector<vector<int>> _2eccs = {};
int timer = 1;
function<void(int, int)> dfs = [&](int u, int from) {
vis[u] = low[u] = timer++;
s.push_back(u);
for(int e : g[u]) {
if(not vis[g(e).v]) {
dfs(g(e).v, e & ~1);
if(vis[u] < low[g(e).v]) {
cut_edge[e] = cut_edge[e ^ 1] = true;
_2eccs.push_back(vector<int>());
do {
_2eccs.back().push_back(s.back()), s.pop_back();
} while(_2eccs.back().back() != g(e).v);
}
low[u] = min(low[u], low[g(e).v]);
} else if((e & ~1) != from and vis[u] > vis[g(e).v]) {
low[u] = min(low[u], vis[g(e).v]);
}
}
};
for(int u = Index; u < g.adj.size(); u++) if(not vis[u]) {
dfs(u, -1);
_2eccs.push_back(vector<int>());
while(not s.empty()) {
_2eccs.back().push_back(s.back()), s.pop_back();
}
}
return {move(cut_edge), move(_2eccs)};
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
graph<0, edge, 1> g(n, m);
edge last_edge;
for(int i = 0; i < m; i++) {
int u, v, w;
cin >> u >> v >> w;
g.add_edge(last_edge = {min(u, v), max(u, v)});
}
graph<0, edge, 1> sp_dag(n);
vector<int> ds(n + 1, lim<int>::max()), dt(n + 1, lim<int>::max());
queue<int> q;
q.push(1);
ds[1] = 0;
while(not q.empty()) {
int u = q.front(); q.pop();
for(int e : g[u]) {
int v = g(e).v;
if(ds[v] > ds[u] + 1) {
ds[v] = ds[u] + 1;
q.push(v);
sp_dag.add_edge({min(u, v), max(u, v)});
} else if(ds[v] == ds[u] + 1) {
sp_dag.add_edge({min(u, v), max(u, v)});
}
}
}
q.push(n);
dt[n] = 0;
while(not q.empty()) {
int u = q.front(); q.pop();
for(int e : g[u]) {
int v = g(e).v;
if(dt[v] > dt[u] + 1) {
dt[v] = dt[u] + 1;
q.push(v);
}
}
}
auto [cut_edge, _2eccs] = find_2eccs(sp_dag);
bool increase = false;
for(int i = 0; i < m - 1; i++) {
edge& sp_edge = sp_dag.edges[i << 1];
increase |= cut_edge[i << 1] and
sp_edge.u != last_edge.u and
sp_edge.v != last_edge.v and
(ds[sp_edge.u] + 1 + dt[sp_edge.v] == ds[n] or ds[sp_edge.v] + 1 + dt[sp_edge.u] == ds[n]);
}
cout << ds[n] + increase << endl;
return 0;
}
Compilation message
Aesthetic.cpp: In instantiation of 'std::pair<std::vector<int>, std::vector<std::vector<int> > > find_2eccs(graph<false, TEdge, Index>&) [with TEdge = edge; bool Index = true]':
Aesthetic.cpp:111:48: required from here
Aesthetic.cpp:60:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
60 | for(int u = Index; u < g.adj.size(); u++) if(not vis[u]) {
| ~~^~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
474 ms |
75852 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
518 ms |
77112 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
447 ms |
109040 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
447 ms |
109040 KB |
Execution killed with signal 11 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
212 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
