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

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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;}
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