# HDU 3639 Hawk-and-chicken (Strong connected component + Tree DP)

Source: Internet
Author: User

First with the strong connected components of the contraction point, after the contraction point, and then re-indent after the block in reverse order of the composition, the value of each block is inside the number of points, then the largest of the votes must be re-composition after the degree of 0 of the block, and then find out the maximum value can be.

The code is as follows:

`#include <iostream> #include <string.h> #include <math.h> #include <queue> #include < algorithm> #include <stdlib.h> #include <map> #include <set> #include <stdio.h>using namespace std; #define LL Long long#define pi ACOs ( -1.0) const int Mod=1e9+7;const int Inf=0x3f3f3f3f;const double eqs=1e-9; const int Maxn=5000+10;const int Maxm=30000+10;int HEAD[MAXN], CNT, LOW[MAXN], DFN[MAXN], BELONG[MAXN], INSTACK[MAXN], St K[MAXN], dp[maxn];int ans, indx, top;struct node{int u, V, next;}        edge[maxm];void Add (int u, int v) {edge[cnt].v=v;        Edge[cnt].next=head[u]; head[u]=cnt++;}        void Tarjan (int u) {low[u]=dfn[u]=++indx;        Instack[u]=1;        Stk[++top]=u;                for (int i=head[u];i!=-1;i=edge[i].next) {int v=edge[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]);                }} if (Low[u]==dfn[u]) {ans++;                        while (1) {int v=stk[top--];                        Belong[v]=ans;                        dp[ans]++;                        instack[v]=0;                if (u==v) break;        }}}void init () {memset (head,-1,sizeof (head));        memset (dfn,0,sizeof (DFN));        memset (instack,0,sizeof (instack));        Memset (Dp,0,sizeof (DP)); Cnt=ans=indx=top=0;} int HEAD1[MAXN], cnt1, VIS[MAXN], IN[MAXN], max1, sum;struct node1{int u, V, next;}        edge1[maxm];void add1 (int u, int v) {edge1[cnt1].v=v;        Edge1[cnt1].next=head1[u]; head1[u]=cnt1++;}        void Dfs (int u) {vis[u]=1;        Sum+=dp[u];                for (int i=head1[u];i!=-1;i=edge1[i].next) {int v=edge1[i].v;                if (!vis[v]) {DFS (v); }}}void init1 () {memset (head1,-1,sizeOf (HEAD1));        memset (vis,0,sizeof (VIS));        memset (In,0,sizeof (in));        cnt1=0; max1=0;}        int C[MAXN], tot, d[maxn];int main () {int T, n, M, I, J, u, V, case=0;        scanf ("%d", &t);                while (t--) {case++;                scanf ("%d%d", &n,&m);                Init ();                        while (m--) {scanf ("%d%d", &u,&v);                Add (U,V);                } for (i=0;i<n;i++) {if (!dfn[i]) Tarjan (i);                } init1 (); for (i=0;i<n;i++) {for (J=head[i];j!=-1;j=edge[j].next) {if (belong[                                        I]!=BELONG[EDGE[J].V]) {add1 (belong[edge[j].v],belong[i]);                                in[belong[i]]++;                }}} memset (D,-1,sizeof (d)); for (i=1;i<=ans;i++) {if (!in[i]) {sum=0;                                memset (vis,0,sizeof (VIS));                                DFS (i);                                D[i]=sum;                        Max1=max (Max1,d[i]);                }} tot=0;                for (i=0;i<n;i++) {if (d[belong[i]]==max1) c[tot++]=i;                } printf ("Case%d:%d\n", case, max1-1);                        for (i=0;i<tot;i++) {printf ("%d", c[i]);                if (i!=tot-1) printf ("");        } puts (""); } return 0;}`

HDU 3639 Hawk-and-chicken (Strong connected component + Tree DP)

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