HDU 3836 Equivalent Sets (Tarjan + contraction point), hdutarjan

HDU 3836 Equivalent Sets (Tarjan + contraction point), hdutarjan
Problem DescriptionTo prove two sets A and B are equivalent, we can first prove A is a subset of B, and then prove B is a subset of, so finally we got that these two sets are equivalent.
You are to prove N sets are equivalent, using the method above: in each step you can prove a set X is a subset of another set Y, and there are also some sets that are already proven to be subsets of some other sets.
Now you want to know the minimum steps needed to get the problem proved.
InputThe input file contains multiple test cases, in each case, the first line contains two integers N <= 20000 and M <= 50000.
Next M lines, each line contains two integers X, Y, means set X in a subset of set Y.
OutputFor each case, output a single integer: the minimum steps needed.
Sample Input

4 03 21 21 3

 
Sample Output

42HintCase 2: First prove set 2 is a subset of set 1 and then prove set 3 is a subset of set 1. 

Strongly linked deflation point: add several sides to form a strongly connected component. After the contraction point is set, the point with a moderate degree of 0 is d_1, And the inbound degree is d_2, the answer is max (d_1, d_2 );

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<limits.h>typedef long long LL;using namespace std;#define REPF( i , a , b ) for ( int i = a ; i <= b ; ++ i )#define REP( i , n ) for ( int i = 0 ; i < n ; ++ i )#define CLEAR( a , x ) memset ( a , x , sizeof a )const int maxn=20000+100;const int maxm=100000;struct node{    int u,v;    int next;}e[maxm];int head[maxn],cntE;int DFN[maxn],low[maxn];int s[maxm],top,index,cnt;int belong[maxn],instack[maxn];int in[maxn],out[maxn];int n,m;void init(){    top=cntE=0;    index=cnt=0;    CLEAR(DFN,0);    CLEAR(head,-1);    CLEAR(instack,0);//    CLEAR(belong,0);}void addedge(int u,int v){    e[cntE].u=u;e[cntE].v=v;    e[cntE].next=head[u];    head[u]=cntE++;}void Tarjan(int u){    DFN[u]=low[u]=++index;    instack[u]=1;    s[top++]=u;    for(int i=head[u];i!=-1;i=e[i].next)    {        int v=e[i].v;        if(!DFN[v])        {            Tarjan(v);            low[u]=min(low[u],low[v]);        }        else if(instack[v])            low[u]=min(low[u],DFN[v]);    }    int v;    if(DFN[u]==low[u])    {        cnt++;        do{            v=s[--top];            belong[v]=cnt;            instack[v]=0;        }while(u!=v);    }}void work(){    REPF(i,1,n)      if(!DFN[i])  Tarjan(i);    if(cnt<=1)    {        puts("0");        return ;    }    CLEAR(in,0);    CLEAR(out,0);    for(int i=0;i<cntE;i++)    {        int u=e[i].u,v=e[i].v;        if(belong[u]!=belong[v])            in[belong[v]]++,out[belong[u]]++;    }    int d_1=0,d_2=0;    REPF(i,1,cnt)    {        if(!in[i])            d_1++;        if(!out[i])            d_2++;    }    printf("%d\n",max(d_1,d_2));}int main(){    int u,v;    while(~scanf("%d%d",&n,&m))    {        init();        for(int i=0;i<m;i++)        {            scanf("%d%d",&u,&v);            addedge(u,v);        }        work();    }    return 0;}

Hdu 1269 tarjan WA explained

No loop call

Hdu1269 forward to star + tarjan do not know where to change the error

Dfs () does not have a loop call