HUST 1017 Exact Cover（舞蹈链模板）

题意：

题意就不多说了，标准的测舞蹈链的题目，花了一下午看了很多博客，终于
看懂了原理，理解之后其实挺清晰地，本来想去看论文原文的，后来还是看
了中文的翻译版，英文太难受了。
推荐两个博客
http://www.cnblogs.com/grenet/p/3145800.html
http://blog.csdn.net/yysdsyl/article/details/4266876
这两个讲的挺清晰的
论文中文版
http://io.sqybi.com/dlxcn/
至于里面有一个优化的措施我个人觉得没啥道理啊- -
我加了反而变慢了
本来我的代码跑的本来就慢，可能是用了STL的缘故。
不过换了一个版本，也就是现在的版本，挺快的

代码：

//
//  Created by  CQU_CST_WuErli
//  Copyright (c) 2016 CQU_CST_WuErli. All rights reserved.
//
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define CLR(x) memset(x,0,sizeof(x))
#define OFF(x) memset(x,-1,sizeof(x))
#define MEM(x,a) memset((x),(a),sizeof(x))
#define BUG cout << "I am here" << endl
#define lookln(x) cout << #x << "=" << x << endl
#define SI(a) scanf("%d",&a)
#define SII(a,b) scanf("%d%d",&a,&b)
#define SIII(a,b,c) scanf("%d%d%d",&a,&b,&c)
#define rep(flag,start,end) for(int flag=start;flag<=end;flag++)
#define Rep(flag,start,end) for(int flag=start;flag>=end;flag--)
#define Lson l,mid,rt<<1
#define Rson mid+1,r,rt<<1|1
#define Root 1,n,1
#define BigInteger bign
const int MAX_L=2005;// For BigInteger
const int INF_INT=0x3f3f3f3f;
const long long INF_LL=0x7fffffff;
const int MOD=1e9+7;
const double eps=1e-9;
const double pi=acos(-1);
typedef long long  ll;
using namespace std;

const int N=1010;

int n,m;

struct Node {
    int right,left,down,up;
    int size;
    int x,y;
};

struct DLX {
    const static int maxn=1000010; // 节点总数
    Node p[maxn];
    int size;                       // 节点标记
    int head[maxn];                 // 行标指针
    int vis[maxn];
    stack<int> Ans;
    int ans;
    void init(int m) {
        for (int i=0;i<=m;i++) {
            p[i].up=p[i].down=i;
            p[i].left=i-1;p[i].right=i+1;
            p[i].size=0;
        }
        p[0].left=m;p[m].right=0;
        OFF(head);
        size=m+1;
        ans=-1;
        while (Ans.size()) Ans.pop();
    }
    void link(int row,int col) {
        p[size].x=row;p[size].y=col;p[col].size++;
        p[size].up=p[col].up;p[p[col].up].down=size;
        p[col].up=size;p[size].down=col;
        if (head[row]<0) head[row]=p[size].left=p[size].right=size;
        else {
            p[size].right=p[head[row]].right;p[p[head[row]].right].left=size;
            p[size].left=head[row];p[head[row]].right=size;
        }
        size++;
    }
    // exact cover
    void remove(int c) {
        p[p[c].right].left=p[c].left;
        p[p[c].left].right=p[c].right;
        for (int i=p[c].down;i!=c;i=p[i].down) {
            for (int j=p[i].right;j!=i;j=p[j].right) {
                p[p[j].down].up=p[j].up;
                p[p[j].up].down=p[j].down;
                p[p[j].y].size--;
            }
        }
    }
    void resume(int c) {
        p[p[c].left].right=c;
        p[p[c].right].left=c;
        for (int i=p[c].up;i!=c;i=p[i].up) {
            for (int j=p[i].left;j!=i;j=p[j].left) {
                p[p[j].down].up=j;
                p[p[j].up].down=j;
                p[p[j].y].size++;
            }
        }

    }
    bool dfs(int cnt) {
        if (ans!=-1) return true;
        if (p[0].right==0) {
            ans=cnt;
            return true;
        }
        int c=0;
        int Min=INF_INT;
        for (int i=p[0].right;i!=0;i=p[i].right)
            if (Min>p[i].size) Min=p[i].size,c=i;
        remove(c);
        for (int i=p[c].down;i!=c;i=p[i].down) {
            Ans.push(p[i].x);
            for (int j=p[i].right;j!=i;j=p[j].right) {
                remove(p[j].y);
            }
            if (dfs(cnt+1)) return true;
            for (int j=p[i].left;j!=i;j=p[j].left) {
                resume(p[j].y);
            }
            Ans.pop();
        }
        resume(c);
        return false;
    }
    // exact cover ends;
    // multiple cover
    void del(int c) {
        for (int i=p[c].down;i!=c;i=p[i].down) {
            p[p[i].right].left=p[i].left;
            p[p[i].left].right=p[i].right;
        }
    }
    void rec(int c) {
        for (int i=p[c].up;i!=c;i=p[i].up) {
            p[p[i].right].left=i;
            p[p[i].left].right=i;
        }
    }
    int h() {
        int ret=0;
        CLR(vis);
        for (int i=p[0].right;i!=0;i=p[i].right) if (!vis[i]) {
            ret++;vis[i]=1;
            for (int j=p[i].down;j!=i;j=p[j].down)
                for (int k=p[j].right;k!=j;k=p[k].right)
                    vis[p[k].y]=1;
        }
        return ret;
    }
    void DFS(int cnt) {
        if (p[0].right==0) ans=min(ans,cnt);
        else if (h()+cntint c=0;
            int Min=INF_INT;
            for (int i=p[c].right;i!=0;i=p[i].right){
                if (p[i].size// lookln(c);
            for (int i=p[c].down;i!=c;i=p[i].down) {
                del(i);
                for (int j=p[i].right;j!=i;j=p[j].right) del(j);
                DFS(cnt+1);
                // BUG;
                for (int j=p[i].left;j!=i;j=p[j].left) rec(j);
                rec(i);
            }
        }
        return;
    }
    // multiple cover ends;
}dlx;
/*
0 1  2  3  4  5  6  7
  8  0  0  9  0  0  10
  11 0  0  12 0  0  0
  0  0  0  13 14 0  15
  0  0  16 0  17 18 0
  0  19 20 0  0  21 22
  0  23 0  0  0  0  24
*/

int main(int argc, char const *argv[]) {
#ifdef LOCAL
    freopen("C:\\Users\\john\\Desktop\\in.txt","r",stdin);
    // freopen("C:\\Users\\john\\Desktop\\out.txt","w",stdout);
#endif
    // BUG;
    while(SII(n,m)==2) {
        dlx.init(m);
        for (int i=1;i<=n;i++){
            int x;SI(x);
            while (x--) {
                int tmp;SI(tmp);
                dlx.link(i,tmp);
            }
        }
        if (dlx.dfs(0)) {
            cout << dlx.ans;
            while (dlx.Ans.size()) {
                cout << ' ' << dlx.Ans.top();
                dlx.Ans.pop();
            }
            cout << endl;
        }
        else puts("NO");
    }
    return 0;
}