#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
const int maxnode = 100010;
const int MaxM = 1010;
const int MaxN = 1010;
struct DLX
{
int n, m, size;//n是行,m是列,size是个数,也是节点标号
int U[maxnode], D[maxnode], R[maxnode], L[maxnode], Row[maxnode], Col[maxnode];
int H[MaxN], S[MaxM];//H是行首指针,S是该列结点总数
int ansd, ans[MaxN];//节点总数,答案
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];//记录节点
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 g;
int main()
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
int n, m;
while (scanf("%d%d", &n, &m) == 2)
{
g.init(n, m);
for (int i = 1; i <= n; i++)
{
int num, j;
scanf("%d", &num);
while (num--)
{
scanf("%d", &j);
g.Link(i, j);
}
}
if (!g.Dance(0))printf("NO\n");
else
{
printf("%d", g.ansd);
for (int i = 0; i < g.ansd; i++)
printf(" %d", g.ans[i]);
printf("\n");
}
}
return 0;
}
1017 Exact cover(Dancing Links模板题)
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转载自blog.csdn.net/qq_40061421/article/details/85262978
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