学步园

题目链接：Click here~~

题意：

又学了一天。呵呵。

解题思路：

先不写思路了，到时候来个总结。

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

const int N = 2e3+5;
const int M = 1e4+5;

struct Vertex
{
    int head;
}V[N];

struct Edge
{
    int v,next;
}E[M];

int n,top,scc,id,dfn[N],low[N],belong[N],sub[N];

bool ok,in[N],cut_p[N],cut_e[M];

stack<int> S;

map<int,int> M1,M2;

void init()
{
    top = n = 0;
    memset(V,-1,sizeof(V));
    M1.clear();
    M2.clear();
}

void add_edge(int u,int v)
{
    if(!M1.count(u))
    {
        M1[u] = n;
        M2[n++] = u;
    }
    u = M1[u];
    if(!M1.count(v))
    {
        M1[v] = n;
        M2[n++] = v;
    }
    v = M1[v];
    E[top].v = v;
    E[top].next = V[u].head;
    V[u].head = top++;
}

void tarjan(int pre,int u)
{
    dfn[u] = low[u] = ++id;
    int cnt = 0;
    //S.push(u);
    for(int i=V[u].head;~i;i=E[i].next)
    {
        int v = E[i].v;
        if(v == pre)
            continue;
        if(!dfn[v])
        {
            ++cnt;
            tarjan(u,v);
            low[u] = min(low[u],low[v]);
            if(u!=pre && dfn[u]<=low[v])
            {
                cut_p[u] = true;
                sub[u]++;
            }
            if(dfn[u] < low[v])
                cut_e[i] = true;
        }
        else
            low[u] = min(low[u],dfn[v]);
    }
    if(u==pre && cnt>1)
    {
        cut_p[u] = true;
        sub[u] = cnt-1;
    }
}

void get_cut()
{
    memset(cut_p,false,sizeof(cut_p));
    memset(cut_e,false,sizeof(cut_e));
    memset(dfn,0,sizeof(dfn));
    memset(sub,0,sizeof(sub));
    for(int i=0;i<n;i++)
        if(!dfn[i])
            tarjan(i,i);
    for(int i=1;i<=1000;i++)
    {
        if(!M1.count(i) || sub[ M1[i] ]==0)
            continue;
        ok = true;
        printf("  SPF node %d leaves %d subnets\n",i,sub[ M1[i] ]+1);
    }
}

int main()
{
    int u,v,ncase=0;
    while(~scanf("%d",&u),u)
    {
        init();
        scanf("%d",&v);
        add_edge(u,v);
        add_edge(v,u);
        while(~scanf("%d",&u),u)
        {
            scanf("%d",&v);
            add_edge(u,v);
            add_edge(v,u);
        }
        if(ncase)
            puts("");
        printf("Network #%d\n",++ncase);
        ok = false;
        get_cut();
        if(!ok)
            puts("  No SPF nodes");
    }
    return 0;
}