Critical Links（连通图 桥）

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=67418#problem/C

求桥裸题：

这个模板好像和KB的还不太一样，有时间研究下

#include <map>#include <set>#include <queue>#include <stack>#include <vector>#include <cmath>#include <cstdio>#include <cstdlib>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int N = 100010;const int M = (N << 2);struct node{int next;int to;//int id;}edge[M];struct BRIDGE{int u;int v;}bridge[M];int head[N];int DFN[N];int low[N];int st[N];bool instack[N];int tot, top, ord, sccnum, cnt;void init (){memset (head, -1, sizeof(head));memset (DFN, -1, sizeof(DFN));memset (low, 0, sizeof(low));memset (instack, 0, sizeof(instack));tot = top = cnt = sccnum = ord = 0;}void addedge (int from, int to){edge[tot].to = to;//edge[tot].id = id;edge[tot].next = head[from];head[from] = tot++;}int cmp (BRIDGE a, BRIDGE b){if (a.u == b.u){return a.v < b.v;}return a.u < b.u;}void tarjan (int u, int fa){DFN[u] = low[u] = ++ord;instack[u] = 1;st[top++] = u;for (int i = head[u]; ~i; i = edge[i].next){int v = edge[i].to;if (v == fa){continue;}if (DFN[v] == -1){tarjan (v, u);low[u] = min (low[v], low[u]);if (low[v] > DFN[u]){bridge[++cnt].u = u;bridge[cnt].v = v;if (bridge[cnt].u > bridge[cnt].v){swap (bridge[cnt].u, bridge[cnt].v);}}}else if (instack[v]){low[u] = min (low[u], DFN[v]);}}if (low[u] == DFN[u]){++sccnum;int v;do{v = st[--top];instack[v] = 0;}while (u != v);}}void solve (int n){for (int i = 1; i <= n; ++i){if (DFN[i] == -1){tarjan(i, -1);}}sort (bridge + 1, bridge + cnt + 1, cmp);printf("%d critical links\n", cnt);for (int i = 1; i <= cnt; ++i){printf("%d - %d\n", bridge[i].u - 1, bridge[i].v - 1);}printf("\n");}int main(){int n;int u, v;int num;while (~scanf("%d", &n)){if (n == 0){printf("0 critical links\n\n");continue;}init();for (int i = 1; i <= n; ++i){scanf("%d", &u);++u;getchar();getchar();scanf("%d", &num);getchar();while (num--){scanf("%d", &v);++v;addedge (u, v);}}solve (n);}return 0;}