lightoj 1026

割边(输出要排序，贼鸡儿坑)

代码如下：

#include <bits/stdc++.h>

using namespace std;

vector<int> k[10010];
int num[10010], vis[10010], low[10010];
pair<int, int>edge[10010];

int __index;

void Init(int n)//初始化
{
    __index = 0;
    for(int i = 0; i < n; i++)
        k[i].clear();
    memset(num, 0, sizeof(num));
    memset(vis, 0, sizeof(vis));
}

void Cut_edge(int cur, int father, int &sum)//dfs求割边
{
    vis[cur] = 1;
    __index++;
    num[cur] = __index;
    low[cur] = __index;
    int n = k[cur].size();
    for(int i = 0; i < n; i++)
    {
        int cnode = k[cur][i];
        if(!num[cnode])
        {
            Cut_edge(cnode, cur, sum);
            low[cur] = min(low[cur], low[cnode]);
            if(num[cur] < low[cnode])
            {
                edge[sum].first = min(cur, cnode);//u<v
                edge[sum].second = max(cur, cnode);
                sum++;
            }
        }
        else if(cnode != father) low[cur] = min(num[cnode], low[cur]);
    }
    return ;
}
int main ()
{
    int t, cnt = 1;
    scanf("%d", &t);
    while(t--)
    {
        int n;
        scanf("%d", &n);
        Init(n);
        //以下为建图
        for(int i = 0; i < n; i++)
        {
            int u, m, v;
            scanf("%d (%d)", &u, &m);
            while(m--)
            {
                scanf("%d", &v);
                k[u].push_back(v);
            }
        }
        int ans = 0;
        for(int i = 0; i < n; i++)
            if(!vis[i])
                Cut_edge(i, i, ans);
        printf("Case %d:\n", cnt++);
        printf("%d critical links\n", ans);
        sort(edge, edge+ans);//输出要升序排序
        for(int i = 0; i < ans; i++)
            printf("%d - %d\n", edge[i].first, edge[i].second);
    }
    return 0;
}