UVA

UVA - 796 

想一想其实写这种题最应该%的是tarjan。

题意+思路： 求割边的模板题，有重边的绝对不是割边，然而这题应该没有有重边的情况。

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#include <sstream>#include <set>using namespace std;const int maxe = 1e4;const int maxn = 2e2;struct node{    int f,to,next;    int isb;    node(){}    node(int d,int a,int b,int c){f = d; to = a; next = b;isb = c;}}edge[maxe << 2];set<pair<int,int> > out;int edgenum = 0,tot = 0,ansnum = 0;int h[maxn], dfn[maxn], low[maxn];int n;void init(){    for(int i = 1; i <= n ; i++)        h[i] = -1, dfn[i] = low[i] = 0;    edgenum = tot = ansnum = 0;    out.clear();}bool cmp(node a,node b){    return a.f < b.f;}void add(int u,int v){    edge[edgenum] = node(u,v,h[u],0);    h[u] = edgenum ++;}int tarjan(int u,int fa){    dfn[u] = low[u] = ++tot;    for(int i = h[u]; ~i; i = edge[i].next)    {        int v = edge[i].to;        //cout << "u v " << u << " " << v << endl;        if(!dfn[v])        {            tarjan(v,u);            low[u] = min(low[u],low[v]);            if(dfn[u] < low[v])            {                int a = u, b = v;                if(u > v) swap(a,b);                out.insert(pair<int,int>(a,b));            }        }        else if(dfn[v] < dfn[u] && v != fa)            low[u] = min(low[u],dfn[v]);    }    return 0;}char strin[1500];int main(){    //freopen("D://in.txt","r", stdin);    int flag = 0;    while(~scanf("%d",&n))    {        init();        for(int i = 0; i < n ; i++)        {            int u,v,vnum;            scanf("%d (%d)",&u,&vnum); u++;            for(int j = 0; j < vnum; j++)            {                scanf("%d",&v);                v++;                add(u,v);            }        }        for(int i = 1; i <= n ; i++)            if(!dfn[i]) tarjan(i,-1);        printf("%d critical links\n",out.size());        for(auto it : out)            printf("%d - %d\n",it.first - 1, it.second - 1 );        printf("\n");    }    return 0;}