POJ1236:Network of Schools

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#include <iostream>#include <stack>#include <string.h>#include <stdlib.h>#include <algorithm>#include <math.h>#include <stdio.h>#define N 1001using namespace std;struct node{    int x,y,next;} eg[100001];int n,tt,cnt,time,ins[N],head[N],low[N],dfn[N],be[N],in[N],ch[N],map[N][N];void init(){    tt=cnt=0;    memset(head,-1,sizeof(head));    memset(ins,0,sizeof(ins));    memset(in,0,sizeof(in));    memset(ch,0,sizeof(ch));    memset(map,0,sizeof(map));    memset(be,0,sizeof(be));}void add(int xx,int yy){    eg[tt].x=xx;    eg[tt].y=yy;    eg[tt].next=head[xx];    head[xx]=tt++;}stack<int>q;void tarjan(int i){    int w;    low[i]=dfn[i]=++time;    q.push(i);    ins[i]=1;    for(int j=head[i]; j!=-1; j=eg[j].next)    {        w=eg[j].y;        if(!dfn[w])        {            tarjan(w);            low[i]=min(low[i],low[w]);        }        else if(ins[w])        {            low[i]=min(low[i],dfn[w]);        }    }    if(dfn[i]==low[i])    {        cnt++;        do        {            w=q.top();            q.pop();            ins[w]=0;            be[w]=cnt;        }        while(!q.empty()&&i!=w);    }}void solve(){    memset(dfn,0,sizeof(dfn));    time=0;    for(int i=1; i<=n; i++)    {        if(!dfn[i])        {            tarjan(i);        }    }    if(cnt==1)    {        printf("1\n0\n");        return ;    }    for(int i=1; i<=n; i++)    {        for(int j=1; j<=n; j++)        {            if(map[i][j]&&be[i]!=be[j])            {                in[be[j]]++;                ch[be[i]]++;            }        }    }    int sum=0;    int count=0;    for(int i=1; i<=cnt; i++)    {        if(in[i]==0) sum++;        if(ch[i]==0) count++;    }    printf("%d\n%d\n",sum,max(sum,count));    return ;}int main(){    int xx;    while(scanf("%d",&n)!=EOF)    {        init();        while(!q.empty())        {            q.pop();        }        for(int i=1; i<=n; i++)        {            while(scanf("%d",&xx)!=EOF&&xx!=0)            {                map[i][xx]=1;                add(i,xx);            }        }        solve();    }    return 0;}

 

POJ1236:Network of Schools