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dancing links code 1-3

一、fzu 1686
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#include<stdio.h>
#include<algorithm>

using namespace std;

const int MAXN = 225;
int L[MAXN*MAXN], R[MAXN*MAXN], U[MAXN*MAXN], D[MAXN*MAXN];
int S[MAXN];
int Col[MAXN*MAXN];
int limit;

void Remove(int x) {
	for (int i = D[x]; i != x; i = D[i]) {
		L[R[i]] = L[i];
		R[L[i]] = R[i];
	}
}
void Resume(int x) {
	for (int i = U[x]; i != x; i = U[i]) {
		L[R[i]] = R[L[i]] = i;
	}
}
int Hash() {
	int ans = 0;
	bool hash[MAXN] = {0};
	for (int c = R[0]; c != 0; c = R[c])
	if (! hash[c]) {
		hash[c] = true;
		ans ++;
		for (int i = D[c]; i != c; i = D[i])
			for (int j = R[i]; j != i; j = R[j])
				hash[Col[j]] = true;
	}
	return ans;
}

bool dfs(int depth) {
	if (depth + Hash() > limit) return false;
	if (R[0] == 0) return true;
	int i, j, c, minnum = INT_MAX;
	for (i = R[0]; i != 0; i = R[i]) {
		if (S[i] < minnum) {
			minnum = S[i];
			c = i;
		}
	}
	for (i = U[c]; i != c; i = U[i]) {
		Remove(i);
		for (j = R[i]; j != i; j = R[j]) Remove(j);
		if (dfs(depth + 1)) {
			for (j = L[i]; j != i; j = L[j]) Resume(j);
			Resume(i);
			return true;
		}
		for (j = L[i]; j != i; j = L[j]) Resume(j);
		Resume(i);
	}
	return false;
}

int solve(int n, int m, int DL[][MAXN], int maxdepth) {
	if (maxdepth > n) maxdepth = n;
	for (int i = 0; i <= m; i ++) {
		L[i] = i - 1;
		R[i] = i + 1;
		U[i] = D[i] = i;
	}
	L[0] = m;
	R[m] = 0;
	int cnt = m + 1;
	memset(S, 0, sizeof (S));
	for (int i = 1; i <= n; i ++) {
		int head = cnt, tail = cnt;
		for (int c = 1; c <= m; c ++) if (DL[i][c]) {
			S[c] ++;
			Col[cnt] = c;
			U[D[c]] = cnt;
			D[cnt] = D[c];
			U[cnt] = c;
			D[c] = cnt;
			L[cnt] = tail;
			R[tail] = cnt;
			R[cnt] = head;
			L[head] = cnt;
			tail = cnt;
			cnt ++;
		}
	}
	int best = 0, worst = maxdepth;
	while (best <= worst) {
		limit = (worst + best) >> 1;
		if (dfs(0)) worst = limit - 1;
		else best = limit + 1;
	}
	return best;
}

int main()
{
	int i,j,k,l,row,col,n,m,n1,m1,mark[MAXN][MAXN],a[33][33],id[33][33];
 
	while(scanf("%d %d",&n,&m) != EOF)
	{
		col = 0;
		for(i=1;i<=n;i++)
			for(j=1;j<=m;j++)
			{
				scanf("%d",&a[i][j]);
				id[i][j] = -1;
				if(a[i][j] == 1) { col++; id[i][j] = col; }
			}
		scanf("%d %d",&n1,&m1);

		row = 0;
		for(i=1;i<=n-n1+1;i++)
			for(j=1;j<=m-m1+1;j++)
			{
				row++;
				for(k=1;k<=col;k++)mark[row][k] = 0;
 
				for(k=i;k<i+n1;k++)
					for(l=j;l<j+m1;l++)
					if(id[k][l] > 0)
						mark[row][id[k][l]] = 1;
			}
 
		printf("%d\n",solve(row, col, mark, row));
	}
	return 0;
}

二、zju 3209
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#include<stdio.h>
#include<algorithm>
#include<math.h>
#include<string.h>

using namespace std;

const int MAXN = 1005;
int L[MAXN*MAXN], R[MAXN*MAXN], U[MAXN*MAXN], D[MAXN*MAXN];
int S[MAXN];
int Col[MAXN*MAXN], Row[MAXN*MAXN],ans,limit,up;


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]) {
		U[D[j]] = j;
		D[U[j]] = j;
		++ S[Col[j]];
	}
	L[R[c]] = c;
	R[L[c]] = c;
}

bool dfs(int depth) {
	if (depth >= ans) return true;
 
	if(R[0] == 0) { if(depth < ans)ans = depth;  return true; }
 
	int i, j, c, minnum = 2000000000, flag = 0;
	for (i = R[0]; i != 0; i = R[i]) {
		if (S[i] < minnum) {
			minnum = S[i];
			c = i;
		}
	}
	Remove(c);
	for (i = U[c]; i != c; i = U[i]) {
		//如果需要的话,在这里记录一组解(Ans[depth] = Row[i])
		for (j = R[i]; j != i; j = R[j]) Remove(Col[j]);
		if (dfs(depth + 1)) flag = 1; //return true;
		for (j = L[i]; j != i; j = L[j]) Resume(Col[j]);
	}
	Resume(c);
	return flag;//false;
}
int solve(int n, int m, int DL[][MAXN]) {
	for (int i = 0; i <= m; i ++) {
		L[i] = i - 1;
		R[i] = i + 1;
		U[i] = D[i] = i;
	}
	L[0] = m;
	R[m] = 0;
	int cnt = m + 1;
	memset(S, 0, sizeof (S));
	for (int i = 1; i <= n; i ++) {
		int head = cnt, tail = cnt;
		for (int c = 1; c <= m; c ++) if (DL[i][c]) {
			S[c] ++;
			Row[cnt] = i;
			Col[cnt] = c;
			U[D[c]] = cnt;
			D[cnt] = D[c];
			U[cnt] = c;
			D[c] = cnt;
			L[cnt] = tail;
			R[tail] = cnt;
			R[cnt] = head;
			L[head] = cnt;
			tail = cnt;
			cnt ++;
		}
	}
	if (dfs(0)) return true;
	return false;
}

int mark[MAXN][MAXN];

int main()
{
	int i,j,k,l,n,m,T,row,col,x1,x2,y1,y2,id[33][33],low;
	scanf("%d",&T);
	while(T--)
	{
		scanf("%d %d %d",&n,&m,&row);
		col = 0;
		for(i=1;i<=n;i++)
			for(j=1;j<=m;j++)
			{
				col++; id[i][j] = col;
			}
 
		for(i=1;i<=row;i++)
			for(j=1;j<=col;j++)mark[i][j] = 0;

		for(i=1;i<=row;i++)
		{
			scanf("%d %d %d %d",&x1,&y1,&x2,&y2);
			x1++; y1++;
			for(k=x1;k<=x2;k++)
				for(l=y1;l<=y2;l++)
				mark[i][id[k][l]] = 1;
		}

		ans = 1000000000;
		if(!solve(row, col, mark))ans = -1;

		printf("%d\n",ans);
	}
	return 0;
}

三、hdu 3529
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#include<stdio.h>
#include<algorithm>

using namespace std;

const int MAXN = 225;
int L[MAXN*MAXN], R[MAXN*MAXN], U[MAXN*MAXN], D[MAXN*MAXN];
int S[MAXN];
int Col[MAXN*MAXN];
int limit;

void Remove(int x) {
	for (int i = D[x]; i != x; i = D[i]) {
		L[R[i]] = L[i];
		R[L[i]] = R[i];
	}
}
void Resume(int x) {
	for (int i = U[x]; i != x; i = U[i]) {
		L[R[i]] = R[L[i]] = i;
	}
}
int Hash() {
	int ans = 0;
	bool hash[MAXN] = {0};
	for (int c = R[0]; c != 0; c = R[c])
	if (! hash[c]) {
		hash[c] = true;
		ans ++;
		for (int i = D[c]; i != c; i = D[i])
		for (int j = R[i]; j != i; j = R[j])
		hash[Col[j]] = true;
	}
	return ans;
}

bool dfs(int depth) {
	if (depth + Hash() > limit) return false;
	if (R[0] == 0) return true;
	int i, j, c, minnum = 2000000000;
	for (i = R[0]; i != 0; i = R[i]) {
		if (S[i] < minnum) {
			minnum = S[i];
			c = i;
		}
	}
	for (i = U[c]; i != c; i = U[i]) {
		Remove(i);
		for (j = R[i]; j != i; j = R[j]) Remove(j);
		if (dfs(depth + 1)) {
			for (j = L[i]; j != i; j = L[j]) Resume(j);
			Resume(i);
			return true;
		}
		for (j = L[i]; j != i; j = L[j]) Resume(j);
		Resume(i);
	}
	return false;
}

int solve(int n, int m, int DL[][MAXN], int maxdepth) {
	if (maxdepth > n) maxdepth = n;
	for (int i = 0; i <= m; i ++) {
			L[i] = i - 1;
			R[i] = i + 1;
			U[i] = D[i] = i;
		}
		L[0] = m;
		R[m] = 0;
		int cnt = m + 1;
		memset(S, 0, sizeof (S));
		for (int i = 1; i <= n; i ++) {
			int head = cnt, tail = cnt;
			for (int c = 1; c <= m; c ++) if (DL[i][c]) {
				S[c] ++;
				Col[cnt] = c;
				U[D[c]] = cnt;
				D[cnt] = D[c];
				U[cnt] = c;
				D[c] = cnt;
				L[cnt] = tail;
				R[tail] = cnt;
				R[cnt] = head;
				L[head] = cnt;
				tail = cnt;
				cnt ++;
			}
		}
		int best = 0, worst = maxdepth;
		while (best <= worst) {
		limit = (worst + best) >> 1;
		if (dfs(0)) worst = limit - 1;
		else best = limit + 1;
	}
	return best;
}

int n,m,M[MAXN][MAXN];

int main()
{
	int i,j,k,l,row,col,idr[33][33],idc[33][33];
   
	char ch[33][33];
	while(scanf("%d %d",&n,&m) != EOF)
	{
		for(i=1;i<=n;i++) scanf("%s",ch[i]+1);
	   
		row = col = 0;
	   
		for(i=1;i<=n;i++)
			for(j=1;j<=m;j++)
			if(ch[i][j] == '.') idr[i][j] = ++row;
			else
			if(ch[i][j] == '#') idc[i][j] = ++col;
		   
		for(i=0;i<=row;i++) for(j=0;j<=col;j++) M[i][j] = 0;
	   
		for(i=1;i<=n;i++)
			for(j=1;j<=m;j++)
			if(ch[i][j] == '.')
			{
				k = i-1; l = j; while(k > 0 && ch[k][l] == '.') k--;
				if(k > 0 && ch[k][l] == '#') M[idr[i][j]][idc[k][l]] = 1;
			   
				k = i+1; l = j; while(k <= n && ch[k][l] == '.') k++;
				if(k <= n && ch[k][l] == '#') M[idr[i][j]][idc[k][l]] = 1;
			   
				k = i; l = j-1; while(l > 0 && ch[k][l] == '.') l--;
				if(l > 0 && ch[k][l] == '#') M[idr[i][j]][idc[k][l]] = 1;
			   
				k = i; l = j+1; while(l <= m && ch[k][l] == '.') l++;
				if(l <= m && ch[k][l] == '#') M[idr[i][j]][idc[k][l]] = 1;
			}
		   
		int ans = solve(row, col, M, col);
		printf("%d\n",ans);
	}
	return 0;  
}