HUST 1017 Exact cover （精确覆盖|Dancing Links模板题）

题意：精确覆盖问题。

思路：测试模板。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<set>
#include<ctime>
#define eps 1e-6
#define LL long long
#define pii pair<int, int>
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;

//const int MAXN = 5000000 + 5;
//const int INF = 0x3f3f3f3f;
const int maxnode = 110000;
const int MaxM = 1010;
const int MaxN = 1010;
struct DLX
{
int n,m,size;
int U[maxnode],D[maxnode],R[maxnode],L[maxnode],Row[maxnode],Col[maxnode];
int H[MaxN], S[MaxM];//H是每一行的头指针，S是每一列的节点数量
int ansd, ans[MaxN];
void init(int _n,int _m)
{
n = _n;
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;
size = m;
for(int i = 1;i <= n;i++)
H[i] = -1;
}
void Link(int r,int c)
{
++S[Col[++size]=c];
Row[size] = r;
D[size] = D[c];
U[D[c]] = size;
U[size] = c;
D[c] = size;
if(H[r] < 0)H[r] = L[size] = R[size] = size;
else
{
R[size] = R[H[r]];
L[R[H[r]]] = size;
L[size] = H[r];
R[H[r]] = size;
}
}
void remove(int c)
{
L[R[c]] = L[c]; R[L[c]] = R[c];
for(int i = D[c];i != c;i = D[i])
for(int j = R[i];j != i;j = R[j])
{
U[D[j]] = U[j];
D[U[j]] = D[j];
--S[Col[j]];
}
}
void resume(int c)
{
for(int i = U[c];i != c;i = U[i])
for(int j = L[i];j != i;j = L[j])
++S[Col[U[D[j]]=D[U[j]]=j]];
L[R[c]] = R[L[c]] = c;
}
//d为递归深度
bool Dance(int d)
{
if(R[0] == 0)
{
ansd = d;
return true;
}
int c = R[0];
for(int i = R[0];i != 0;i = R[i])
if(S[i] < S[c])
c = i;
remove(c);
for(int i = D[c];i != c;i = D[i])
{
ans[d] = Row[i];
for(int j = R[i]; j != i;j = R[j])remove(Col[j]);
if(Dance(d+1))return true;
for(int j = L[i]; j != i;j = L[j])resume(Col[j]);
}
resume(c);
return false;
}
} dlx;

int main() {
//freopen("input.txt", "r", stdin);
int n, m;
while(cin >> n >> m) {
dlx.init(n, m);
for(int i = 1; i <= n; i++) {
int cnt;
scanf("%d", &cnt);
for(int j = 1; j <= cnt; j++) {
int tmp;
scanf("%d", &tmp);
dlx.Link(i, tmp);
}
}
bool ok = dlx.Dance(0);
if(!ok) puts("NO");
else {
printf("%d", dlx.ansd);
for(int i = 0; i < dlx.ansd; i++) printf(" %d", dlx.ans[i]);
puts("");
}
}
return 0;
}