POJ 1523 SPF（求割点）

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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;}