神龙的难题 （FZU 1686）

  课重复覆盖的模板

#include <iostream>
#include<stdio.h>
#include<cmath>
#include<string.h>
#include<algorithm>
#include<string>
#include<vector>
using namespace std;
const int inf = 0x3fffffff;
const int maxn = 15*15+10;
const int maxnode = maxn*maxn;
struct DLX
{
    int n,m,sz;
    int U[maxnode],D[maxnode],R[maxnode],L[maxnode],row[maxnode],col[maxnode];
    int H[maxn],S[maxn];
    int ans;
    void init(int n,int m)
    {
        this->n=n;
        this->m=m;
        for(int i = 0; i <= m; i++)
        {
            S[i] = 0;
            U[i] = D[i] = i;
            L[i] = i-1;
            R[i] = i+1;
        }
        R[m] = 0;
        L[0] = m;
        sz = m;
        for(int i = 1; i <= n; i++)H[i] = -1;
    }
    void Link(int r,int c)
    {
        ++S[col[++sz]=c];
        row[sz] = r;
        U[sz] = U[c];
        D[U[c]] = sz;
        D[sz] = c;
        U[c] = sz;
        if(H[r] < 0)H[r] = L[sz] = R[sz] = sz;
        else
        {
            L[sz] = L[H[r]];
            R[L[H[r]]] = sz;
            R[sz] = H[r];
            L[H[r]] = sz;
        }
    }
    #define FOR(i,A,s) for(int i=A[s];i!=s;i=A[i])
    void remove(int c)
    {
//        L[R[c]]=L[c];
//        R[L[c]]=R[c];
        FOR(i,D,c)
        {
            L[R[i]]=L[i];
            R[L[i]]=R[i];
        }
    }
    void restore(int c)
    {
        FOR(i,U,c)
        {
            L[R[i]]=i;
            R[L[i]]=i;
        }
//        L[R[c]]=c;
//        R[L[c]]=c;
    }
    bool v[maxn];
    int f()
    {
        int ret = 0;
        for(int c = R[0]; c != 0; c = R[c]) v[c] = true;
        for(int c = R[0]; c != 0; c = R[c])
            if(v[c])
            {
                ret++;
                v[c] = false;
                for(int i = D[c]; i != c; i = D[i])
                    for(int j = R[i]; j != i; j = R[j])
                        v[col[j]] = false;
            }
        return ret;
    }
    void dfs(int d)
    {
        if(d+f()>=ans)
            return ;
        if(R[0]==0)
        {
            ans=min(ans,d);        //找到了解
            return ;
        }
        //找到S最小的列c
        int c=R[0];               //第一个为删除的列
        FOR(i,R,0)
        if(S[i]<S[c])
            c=i;

        FOR(i,D,c)
        {
            remove(i);
            FOR(j,R,i) remove(j);
            dfs(d+1);
            FOR(j,L,i) restore(j);
            restore(i);
        }

        return;
    }
    int solve()
    {
        ans=inf;
        dfs(0);
        return ans;
    }
};

int G[20][20];
int id[20][20];
int main()
{
    int n,m;

    while(~scanf("%d %d",&n,&m))
    {
        int cnt=0;
        memset(id,-1,sizeof id);
        for(int i=0; i<n; i++)
        {
            for(int j=0; j<m; j++)
            {
                scanf("%d",&G[i][j]);
                if(G[i][j])
                {
                    id[i][j]=++cnt;
                }
            }
        }
        DLX X;
        X.init(n*m,cnt);
        int l,w;
        scanf("%d %d",&l,&w);
        int r=1;
        for(int i=0; i+l<=n; i++)
            for(int j=0; j+w<=m; j++)
            {
                for(int k=0; k<l; k++)
                    for(int e=0; e<w; e++)
                        if(G[i+k][j+e])
                            X.Link(r,id[i+k][j+e]);
                r++;
            }
        printf("%d\n",X.solve());
    }

    return 0;
}