ZOJ 3209 Treasure Map （DLX精确覆盖）

#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;
int U[maxnode],D[maxnode],R[maxnode],L[maxnode],Row[maxnode],Col[maxnode];
int H[MaxN], S[MaxM];
int ansd, ans[MaxN];//保存答案和解的方案
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];
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
void Dance(int d)
{
/*此处根据题目可考虑适当剪枝*/
if(R[0] == 0)
{
if(ansd == -1) ansd = d;//ansd初始化为-1，若可通过最后的值判断有没有解
else if(ansd > d) ansd = d;//寻找最优解，可根据题目更改条件
return ;
}
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];//记录解的方案
for(int j = R[i]; j != i; j = R[j])remove(Col[j]);
Dance(d+1);
for(int j = L[i]; j != i; j = L[j])resume(Col[j]);
}
resume(c);
}
};

DLX g;
int main()
{
int T;
int n,m,p;
scanf("%d",&T);
while(T--)
{
scanf("%d%d%d",&n,&m,&p);
g.init(p,n*m);
int x1,y1,x2,y2;
for(int k = 1;k <= p;k++)
{
scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
for(int i = x1+1;i <= x2;i++)
for(int j = y1+1;j <= y2;j++)
g.Link(k,j + (i-1)*m);
}
g.ansd = -1;
g.Dance(0);
printf("%d\n", g.ansd);
}
return 0;
}