hdu 3529 Bomberman - Just Search! 【重复覆盖】

http://acm.hdu.edu.cn/showproblem.php?pid=3529

题目大意：最少需要几个炸弹（先后放）能够把所有的墙炸掉。

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <cmath>
#include <queue>
using namespace std;
template <class T> void checkmin(T &t,T x) {if(x < t) t = x;}
template <class T> void checkmax(T &t,T x) {if(x > t) t = x;}
template <class T> void _checkmin(T &t,T x) {if(t==-1) t = x; if(x < t) t = x;}
template <class T> void _checkmax(T &t,T x) {if(t==-1) t = x; if(x > t) t = x;}
typedef pair <int,int> PII;
typedef pair <double,double> PDD;
typedef long long ll;
#define foreach(it,v) for(__typeof((v).begin()) it = (v).begin(); it != (v).end ; it ++)
const int N = 200 , V = 1020;
int U[V] , D[V] , L[V] , R[V] , C[V];
int H[N] , S[N] , visit[17][17];
int size , n , m , ak;
int rr , cc; // 代表0-1矩阵的行和列
char mp[17][17];
void Link(int r,int c) {
    S[c] ++; C[size] = c;
    U[size] = U[c]; D[U[c]] = size;
    D[size] = c; U[c] = size;
    if(H[r] == -1) H[r]=L[size]=R[size]=size;
    else {
        L[size]=L[H[r]];R[L[H[r]]]=size;
        R[size]=H[r];L[H[r]]=size;
    }
    size ++;
}
void remove(int c) { //delete column
    int i;
    for(i=D[c];i!=c;i=D[i])
        L[R[i]]=L[i],R[L[i]]=R[i];
}
void resume(int c) {
    int i;
    for(i=U[c];i!=c;i=U[i])
        L[R[i]] = R[L[i]] = i;
}
int h() {
    int i,j,k,count = 0;
    bool hash[N];
    memset(hash,0,sizeof(hash));
    for(i=R[0];i;i=R[i]) {
        if(hash[i]) continue;
        hash[i] = 1;
        count ++;
        for(j=D[i];j!=i;j=D[j])
            for(k=R[j];k!=j;k=R[k])
                hash[C[k]] = 1;
    }
    return count;
}
void Dance(int k) {
    int i , j ,Min , c;
    if(h()+k >= ak) return;
    if(!R[0]) {
        checkmin(ak , k);
        return;
    }
    for(Min=N,i=R[0];i;i=R[i])
        if(S[i] < Min) Min = S[i] , c = i;
    for(i=D[c];i!=c;i=D[i]) {
        remove(i);
        for(j=R[i];j!=i;j=R[j])
            remove(j);
        Dance(k+1);
        for(j=L[i];j!=i;j=L[j])
            resume(j);
        resume(i);
    }
}
int main() {
    while(~scanf("%d%d",&n,&m)) {
        cc = 0;
        memset(visit,0,sizeof(visit));
        for(int i=0;i<n;i++) scanf("%s",mp[i]);
        for(int i=0;i<n;i++)
            for(int j=0;j<m;j++)
                if(mp[i][j] == '#')
                    visit[i][j] = ++cc;
        for(int i=0;i<=cc;i++) {
            S[i] = 0;
            D[i] = U[i] = i;
            L[i+1] = i; R[i] = i+1;
        }
        R[cc] = 0;
        size = cc + 1;
        memset(H,-1,sizeof(H));
        rr = 0;
        for(int i=1;i<n-1;i++) {
            for(int j=1;j<m-1;j++) {
                if(mp[i][j] == '.') {
                    rr ++;
                    int k1 , k2;
                    k1 = i-1;k2 = j;
                    while(mp[k1][k2]=='.') k1--;
                    if(mp[k1][k2]=='#') Link(rr,visit[k1][k2]);
                    k1 = i+1;k2 = j;
                    while(mp[k1][k2]=='.') k1++;
                    if(mp[k1][k2]=='#') Link(rr,visit[k1][k2]);
                    k1 = i;k2 = j-1;
                    while(mp[k1][k2]=='.') k2--;
                    if(mp[k1][k2]=='#') Link(rr,visit[k1][k2]);
                    k1 = i;k2 = j+1;
                    while(mp[k1][k2]=='.') k2++;
                    if(mp[k1][k2]=='#') Link(rr,visit[k1][k2]);
                }
            }
        }
        ak = N;
        Dance(0);
        printf("%d\n" , ak);
    }
    return 0;
}