ZOJ 3209

精确覆盖

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
using namespace std;const int maxn=920;
const int maxnode=920*550;
const int maxr=550;
int ans;
struct DLX
{int n , sz;                                                 // 行数，节点总数int S[maxn];                                                // 各列节点总数int row[maxnode],col[maxnode];                              // 各节点行列编号int L[maxnode],R[maxnode],U[maxnode],D[maxnode];            // 十字链表int ansd;                                         // 解void init(int n ){this->n = n ;for(int i = 0 ; i <= n; i++ ){U[i] = i ;D[i] = i ;L[i] = i - 1;R[i] = i + 1;}R[n] = 0 ;L[0] = n;sz = n + 1 ;memset(S,0,sizeof(S));}void addRow(int r,vector<int> c1){int first = sz;for(int i = 0 ; i < c1.size(); i++ ){int c = c1[i];L[sz] = sz - 1 ; R[sz] = sz + 1 ; D[sz] = c ; U[sz] = U[c];D[U[c]] = sz; U[c] = sz;row[sz] = r; col[sz] = c;S[c] ++ ; sz ++ ;}R[sz - 1] = first ; L[first] = sz - 1;}// 顺着链表A，遍历除s外的其他元素#define FOR(i,A,s) for(int i = A[s]; i != s ; i = A[i])void remove(int c){L[R[c]] = L[c];R[L[c]] = R[c];FOR(i,D,c)FOR(j,R,i) {U[D[j]] = U[j];D[U[j]] = D[j];--S[col[j]];}}void restore(int c){FOR(i,U,c)FOR(j,L,i) {++S[col[j]];U[D[j]] = j;D[U[j]] = j; }L[R[c]] = c;R[L[c]] = c;}void dfs(int d){if(d>=ans) return ;if(R[0] == 0 ){ansd = d;ans=min(ans,ansd);}// 找S最小的列cint c = R[0] ;FOR(i,R,0) if(S[i] < S[c]) c = i;remove(c);FOR(i,D,c){FOR(j,R,i) remove(col[j]);dfs(d + 1);FOR(j,L,i) restore(col[j]);}restore(c);}bool solve(){dfs(0);}
};DLX solver;int main(){int T; int n,m ,p; int xx1,xx2,yy1,yy2;vector<int>colmuns;scanf("%d",&T);while(T--){ans=(1<<30);scanf("%d%d%d",&n,&m,&p);solver.init(n*m);for(int k=1;k<=p;k++){colmuns.clear();scanf("%d%d%d%d",&xx1,&yy1,&xx2,&yy2);for(int i=xx1+1;i<=xx2;i++){for(int j=yy1+1;j<=yy2;j++){colmuns.push_back((i-1)*m+j);}}solver.addRow(k,colmuns);}solver.solve();if(ans==(1<<30)) printf("-1\n");else printf("%d\n",ans);}return 0;
}