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题意：有一个网络有一些边相互连接，现在有Q次操作，求每次操作后的桥的个数

分析：开始竟然不知道还有LCA这么个东西.......

*****************************************************************

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;

const int MAXN = 1e5+5;

/********添加边*************/
struct Edage{int v, next, used;}e[MAXN<<2];
int Head[MAXN], cnt;
void AddEdge(int u, int v)
{
    e[cnt].v = v;
    e[cnt].next = Head[u];
    e[cnt].used = false;
    Head[u] = cnt++;
}
/***********Tarjan算法变量**********/
int dfn[MAXN], low[MAXN], Index;
int fa[MAXN];
int isbridge[MAXN], nbridge;

void InIt(int N)
{
    cnt = Index = nbridge = 0;

    for(int i=0; i<=N; i++)
    {
        Head[i] = -1;
        dfn[i] = 0;
        isbridge[i] = false;
    }
}
void Tarjan(int u, int father)
{
    int v;

    low[u] = dfn[u] = ++Index;
    fa[u] = father;

    for(int j=Head[u]; j!=-1; j=e[j].next)
    {
        if(e[j].used == false)
        {
            e[j].used = e[j^1].used = true;
            v = e[j].v;
            if( !dfn[v] )
            {
                Tarjan(v, u);
                low[u] = min(low[u], low[v]);

                if( low[v] > dfn[u] )
                {
                    isbridge[v] = true;
                    nbridge++;
                }
            }
            else
                low[u] = min(low[u], dfn[v]);
        }
    }
}

void LCA(int u, int v)
{
    if(dfn[u] < dfn[v])
        swap(u, v);

    while(dfn[u] > dfn[v])
    {
        if(isbridge[u])nbridge--;
        isbridge[u] = false;
        u = fa[u];
    }

    while(u != v)
    {
        if(isbridge[u])nbridge--;
        if(isbridge[v])nbridge--;
        isbridge[u] = isbridge[v] = false;

        u = fa[u], v = fa[v];
    }
}

int main()
{
    int N, M, t=1;

    while(scanf("%d%d", &N, &M), N+M)
    {
        int u, v;

        InIt(N);

        while(M--)
        {
            scanf("%d%d", &u, &v);
            AddEdge(u, v);
            AddEdge(v, u);
        }

        Tarjan(1, 1);

        scanf("%d", &M);

        printf("Case %d:
", t++);
        while(M--)
        {
            scanf("%d%d", &u, &v);
            LCA(u, v);
            printf("%d
", nbridge);
        }

        printf("
");
    }

    return 0; 

}