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| struct SPFA {
struct node {
int to, w;
};
int n;
std::vector<std::vector<node>> adj;
std::vector<int> dist;
std::vector<int> cnt;
std::vector<int> st;
SPFA() {}
SPFA(int n) {
init(n);
}
void init(int n) {
this -> n = n;
adj.resize(n);
dist.assign(n, INF);
cnt.assign(n, 0);
st.assign(n, 0);
}
void addEdge(int u, int v, int w) {
adj[u].push_back({v, w});
}
bool spfa(int start = 0) {
dist[start] = 0;
std::queue<int> que;
que.push(start);
st[start] = 1;
while (que.size()) {
auto u = que.front();
que.pop();
st[u] = 0;
for (auto [v, w] : adj[u]) {
if (dist[v] > dist[u] + w) {
dist[v] = dist[u] + w;
cnt[v] = cnt[u] + 1;
if (cnt[v] >= n) {
return false;
}
if (!st[v]) {
que.push(v);
st[v] = 1;
}
}
}
}
return true;
}
};
|
