Get Luffy Out * HDU

题意：

　　英语限制了我的行动力。。。。就是两个钥匙不能同时用，两个锁至少开一个

建个图 二分就好了。。。emm。。。。dfs  开头low 写成sccno  然后生活失去希望。。。

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <cctype>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <bitset>
#define rap(i, a, n) for(int i=a; i<=n; i++)
#define rep(i, a, n) for(int i=a; i<n; i++)
#define lap(i, a, n) for(int i=n; i>=a; i--)
#define lep(i, a, n) for(int i=n; i>a; i--)
#define rd(a) scanf("%d", &a)
#define rlld(a) scanf("%lld", &a)
#define rc(a) scanf("%c", &a)
#define rs(a) scanf("%s", a)
#define pd(a) printf("%d
", a);
#define plld(a) printf("%lld
", a);
#define pc(a) printf("%c
", a);
#define ps(a) printf("%s
", a);
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 10010, INF = 0x7fffffff, LL_INF = 0x7fffffffffffffff;
int n, m;
vector<int> G[maxn];
int sccno[maxn], vis[maxn], low[maxn], scc_cnt, scc_clock;
stack<int> S;

struct node
{
    int x, y;
}Node[maxn], Edge[maxn];
void init()
{
    mem(sccno, 0);
    mem(vis, 0);
    mem(low, 0);
    scc_clock = scc_cnt = 0;
    for(int i = 0; i < maxn; i++) G[i].clear();
}

void dfs(int u)
{
    vis[u] = low[u] = ++scc_clock;
    S.push(u);
    for(int i = 0; i < G[u].size(); i++)
    {
        int v = G[u][i];
        if(!vis[v])
        {
            dfs(v);
            low[u] = min(low[v], low[u]);
        }
        else if(!sccno[v])
            low[u] = min(low[u], vis[v]);
    }
    if(vis[u] == low[u])
    {
        scc_cnt++;
        for(;;)
        {
            int x = S.top(); S.pop();
            sccno[x] = scc_cnt;
            if(x == u) break;
        }
    }
}

bool check()
{
    for(int i = 0; i <= n * 4 - 2; i += 2)
        if(sccno[i] == sccno[i + 1])
        {
            return false;
        }
    return true;
}

void build(int mid)
{
    for(int i = 0; i < n; i++)
    {
        int u = Edge[i].x, v = Edge[i].y;
        G[u << 1 | 1].push_back(v << 1);
        G[v << 1 | 1].push_back(u << 1);
    }

    for(int i = 0; i < mid; i++)
    {
        int u = Node[i].x, v = Node[i].y;
        G[u << 1].push_back(v << 1 | 1);
        G[v << 1].push_back(u << 1 | 1);
    }
}

int main()
{
    int u, v;
    while(cin >> n >> m && n + m)
    {
        init();
        for(int i = 0; i < n; i++)
        {
            cin >> Edge[i].x >> Edge[i].y;
        }
        for(int i = 0; i < m; i++)
        {
            cin >> Node[i].x >> Node[i].y;
        }
        int l = 1, r = m, ans;
        while(l <= r)
        {
            init();
            int mid = (l + r) / 2;
            build(mid);
            for(int i = 0; i <= n * 4 - 2; i++)
                if(!vis[i]) dfs(i);
            if(check()) l = mid + 1;
            else r = mid - 1;
        }
        cout << r << endl;

    }

    return 0;
}