Tarjan 求强连通分量
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#include
#include
#include
using namespace std;
const int N = 1e4 + 1e3;
int n, m, cnt, dfn[N], low[N], inq[N];
int stk[N], tp, c[N], cnt_c, sz[N];
vector
ed[N], ed_c[N]; void tarjan(int u) { inq[u] = 1; stk[++tp] = u; dfn[u] = low[u] = ++cnt; for (int i = 0, up = ed[u].size(); i < up; ++i) { if (!dfn[ed[u][i]]) { tarjan(ed[u][i]); low[u] = min(low[u], low[ed[u][i]]); } else if (inq[ed[u][i]]) low[u] = min(low[u], low[ed[u][i]]); } if (dfn[u] == low[u]) { ++cnt_c; while (1) { c[stk[tp]] = cnt_c; inq[stk[tp]] = 0; sz[cnt_c]++; tp--; if (stk[tp + 1] == u) break; } } } int main() { scanf("%d%d", &n, &m); for (int i = 1; i <= m; ++i) { int u, v; scanf("%d%d", &u, &v); ed[u].push_back(v); } for (int i = 1; i <= n; ++i) if (!dfn[i]) tarjan(i); for (int i = 1; i <= n; ++i) { for (int j = 0, up = ed[i].size(); j < up; ++j) { if (c[i] != c[ed[i][j]]) { ed_c[c[i]].push_back(c[ed[i][j]]); } } } int flag =0, ans = 0; for (int i = 1; i <= cnt_c; ++i) { if (!ed_c[i].size()) flag++, ans = sz[i]; } if (flag > 1) return puts("0"), 0; printf("%d\n", ans); }
Tarjan 求点双联通分量
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```
#include
#include
#include
#include
using namespace std; const int N = 1e5 + 5; int dfn[N], low[N], cnt, n, m; int stk[N], tp, root, cut[N], cnt_DCC; vector
ed[N], cut_node, DCC[N]; void tarjan(int u) { int flag = 0; dfn[u] = low[u] = ++ cnt; stk[++tp] = u; for (int i = 0, up = ed[u].size(); i < up; ++i) { if (!dfn[ed[u][i]]) { tarjan(ed[u][i]); low[u] = min(low[u], low[ed[u][i]]); if (low[ed[u][i]] >= dfn[u]) { ++flag; if (root != u || flag > 1) { cut[u] = 1; } ++cnt_DCC; while (1) { DCC[cnt_DCC].push_back(stk[tp]); tp--; if (stk[tp + 1] == ed[u][i]) break; } DCC[cnt_DCC].push_back(u); } } else low[u] = min(low[u], dfn[ed[u][i]]); } } int main() { scanf("%d%d", &n, &m); for (int i = 1; i <= m; ++i) { int u, v; scanf("%d%d", &u, &v); ed[u].push_back(v); ed[v].push_back(u); } for (int i = 1; i <= n; ++i) if (!dfn[i]) tarjan(root = i); for (int i = 1; i <= n; ++i) if (cut[i]) cut_node.push_back(i); printf("%d\n", (int)cut_node.size()); for (int i = 0, up = cut_node.size(); i < up; ++i) printf("%d ", cut_node[i]); puts(""); for (int i = 1; i <= cnt_DCC; ++i) { printf("e-DCC %d ", i); for (int j = 0, up = DCC[i].size(); j < up; ++j) printf("%d ", DCC[i][j]); puts(""); } } ```
SPFA
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```
#include
#include
size=
#include
#include
#include
using namespace std; typedef long long LL; const int N = 1e4 + 5, M = 1e6; int head[N], tot, n, m, S, vis[N]; LL dis[N]; queue
que; struct edge { int nxt, to, w; }e[M]; void add(int u, int v, int w) { e[++tot].nxt = head[u]; e[tot].to = v; e[tot].w = w; head[u] = tot; } void SPFA() { dis[S] = 0; que.push(S); for (int u; !que.empty(); ) { u = que.front(); que.pop(); vis[u] = 0; for (int i = head[u]; i; i = e[i].nxt) { int nt = e[i].to; if (dis[nt] > dis[u] + e[i].w) { dis[nt] = dis[u] + e[i].w; if (!vis[nt]) que.push(nt), vis[nt] = 1; } } } } int main() { scanf("%d%d%d", &n, &m, &S); for (int i = 1; i <= m; ++i) { int u, v, w; scanf("%d%d%d", &u, &v, &w); add(u, v, w); } memset(dis, 120, sizeof(dis)); SPFA(); for (int i = 1; i <= n; ++i) { if (dis[i] == dis[0]) printf("%lld ", 2147483647LL); else printf("%lld ", dis[i]); } } ```