用最少的矩阵覆盖n*m的地图。注意矩阵不能互相覆盖。

这里显然是一个精确覆盖，但因为矩阵拼接过程中，有公共的边，这里须要的技巧就是把矩阵的左边和以下截去一个单位。

#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>
#include <assert.h>
using namespace std;
const int maxnode = 550005;
const int MaxM = 999;
const int MaxN = 555;
int K,n,m;
void print(int x)
{printf("(%d %d)\n",x%(n+1)==0?

n:(x%(n+1)-1),x%(n+1)==0?

x/(n+1)-1:x/(n+1)); } 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 ands,ans[MaxN],ANS; void init(int _n,int _m) { ANS=0x3f3f3f3f; 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) { int i,j; L[R[c]]=L[c]; R[L[c]]=R[c]; for(i=D[c]; i!=c; i=D[i]) { for(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) { int i,j; for(i=U[c]; i!=c; i=U[i]) { for(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 v[maxnode]; int f() { int ret = 0; for(int c = R[0]; c != 0; c = R[c])v[c] = true; for(int c = R[0]; c != 0; c = R[c]) if(v[c]) { ret++; v[c] = false; for(int i = D[c]; i != c; i = D[i]) for(int j = R[i]; j != i; j = R[j]) v[Col[j]] = false; } return ret; } void Dance(int d) { if(d+f()>=ANS) return; if(R[0] == 0) { ANS=min(ANS,d); 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]) { 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); } } g; int main() { int cas,x1,y1,x2,y2,k; scanf("%d",&cas); while(cas--) { scanf("%d%d%d",&n,&m,&k); g.init(k,n*m); for(int q=1; q<=k; q++) { 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(q,j+(i-1)*m); } g.Dance(0); if(g.ANS==0x3f3f3f3f) g.ANS=-1; printf("%d\n",g.ANS); } return 0; }