bzoj 1066: [SCOI2007]蜥蜴

Posted 2021-02-05 lxy8584099

最大流

 

/**************************************************************
    Problem: 1066
    User: lxy8584099
    Language: C++
    Result: Accepted
    Time:80 ms
    Memory:7164 kb
****************************************************************/
 
/*
    最大流  
    每个柱子拆两半 流量为高度
    柱子能到达的 一个连另一个 inf  能跳出去的inf
    实在不想打了。。。炒粉黄SIR的代码 
*/
#include<iostream>
#include<cstdio>
#include<cstring>
#define inf 0x7fffffff
using namespace std;
struct data{int to,next,v;}e[500001];
int r,c,d,cnt=1,ans,mp[21][21],mark[21][21],q[802],h[802],head[802];
void ins(int u,int v,int w)
{cnt++;e[cnt].to=v;e[cnt].next=head[u];head[u]=cnt;e[cnt].v=w;}
void insert(int u,int v,int w)
{ins(u,v,w);ins(v,u,0);}
bool judge(int x1,int y1,int x2,int y2)
{
    if(((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))<=(d*d)&&mp[x1][y1]&&mp[x2][y2])return 1;
    return 0;
}
void build()
{
     for(int x1=1;x1<=r;x1++)
        for(int y1=1;y1<=c;y1++)
           for(int x2=x1-d;x2<=x1+d;x2++)
              for(int y2=y1-d;y2<=y1+d;y2++)
     if(judge(x1,y1,x2,y2)&&(x1!=x2||y1!=y2))insert(mark[x1][y1]+400,mark[x2][y2],inf); 
     for(int i=1;i<=r;i++)
        for(int j=1;j<=c;j++)
           if(mp[i][j])insert(mark[i][j],mark[i][j]+400,mp[i][j]);
 } 
bool bfs()
{
     memset(h,-1,sizeof(h));
     int t=0,w=1,i,now;q[0]=h[0]=0;
     while(t<w)
     {
               now=q[t];t++;i=head[now];
               while(i)
               {
                       if(e[i].v&&h[e[i].to]==-1)
                       {
                           h[e[i].to]=h[now]+1;
                           q[w++]=e[i].to; 
                           }
                       i=e[i].next; 
                       }
               }
     if(h[801]==-1)return 0;return 1;
 }
int dfs(int x,int f)
{
    if(x==801)return f;
    int i=head[x],used=0,w;
    while(i)
    {
            if(e[i].v&&h[e[i].to]==h[x]+1)
            {
                w=f-used;w=dfs(e[i].to,min(w,e[i].v));
                e[i].v-=w;e[i^1].v+=w;
                used+=w;if(used==f)return f;
                                          }
            i=e[i].next;
            }
    if(!used)h[x]=-1;
    return used;
}
void dinic(){while(bfs())ans-=dfs(0,inf);}
int main()
{
    scanf("%d%d%d",&r,&c,&d);
    char ch[21];
    for(int i=1;i<=r;i++)
    {
       scanf("%s",ch);
       for(int j=1;j<=c;j++)
           mp[i][j]=ch[j-1]-‘0‘;
          }
    int tot=0;
    for(int i=1;i<=r;i++)
       for(int j=1;j<=c;j++)
       {tot++;mark[i][j]=tot;} 
    for(int i=1;i<=r;i++)
    {
       scanf("%s",ch);
       for(int j=1;j<=c;j++)
           if(ch[j-1]==‘L‘)
             {insert(0,mark[i][j],1);ans++;}
          }
    for(int i=1;i<=d;i++)
       for(int j=d+1;j<=r-d;j++)
       {
          insert(mark[j][i]+400,801,inf);
          insert(mark[j][c-i+1]+400,801,inf);
          }
    for(int i=1;i<=d;i++)
       for(int j=1;j<=c;j++)
       {
          insert(mark[i][j]+400,801,inf);
          insert(mark[r-i+1][j]+400,801,inf);
          }
    build();
    dinic();
    printf("%d",ans);
    return 0;
}