Going Home HDU - 1533

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费用流模板

一开始建的图太烂了 每个点和四周的点建边 其实只对m与H建边即可 边的费用即为两点曼哈顿距离

#include <bits/stdc++.h>
using namespace std;
#define N 0x3f3f3f3f

struct node1
{
    int v;
    int w;
    int c;
    int next;
};

struct node2
{
    int x;
    int y;
};

queue <int> que;
node1 edge[40010];
node2 pre1[10010],pre2[10010];
int first[10010],dis[10010],book[10010],pre[10010];
char mp[110][110];
int n,m,num,s,e,cnt1,cnt2;

void addedge(int u,int v,int w,int c)
{
    edge[num].v=v;
    edge[num].w=w;
    edge[num].c=c;
    edge[num].next=first[u];
    first[u]=num++;
    return;
}

void build()
{
    int next[4][2]={0,-1,-1,0,0,1,1,0};
    int i,j,k,tx,ty,u,v;
    s=n*m+1,e=n*m+2,cnt1=0,cnt2=0;
    for(i=0;i<n;i++)
    {
        for(j=0;j<m;j++)
        {
            if(mp[i][j]=='m')
            {
                cnt1++;
                pre1[cnt1].x=i;
                pre1[cnt1].y=j;
            }
            else if(mp[i][j]=='H')
            {
                cnt2++;
                pre2[cnt2].x=i;
                pre2[cnt2].y=j;
            }
        }
    }
    memset(first,-1,sizeof(first));
    num=0;
    for(i=1;i<=cnt1;i++)
    {
        u=s,v=pre1[i].x*m+pre1[i].y+1;
        addedge(u,v,1,0);
        addedge(v,u,0,0);
    }
    for(i=1;i<=cnt2;i++)
    {
        u=pre2[i].x*m+pre2[i].y+1,v=e;
        addedge(u,v,1,0);
        addedge(v,u,0,0);
    }
    for(i=1;i<=cnt1;i++)
    {
        for(j=1;j<=cnt2;j++)
        {
            u=pre1[i].x*m+pre1[i].y+1,v=pre2[j].x*m+pre2[j].y+1;
            addedge(u,v,1,abs(pre1[i].x-pre2[j].x)+abs(pre1[i].y-pre2[j].y));
            addedge(v,u,0,-abs(pre1[i].x-pre2[j].x)-abs(pre1[i].y-pre2[j].y));
        }
    }
    return;
}

int spfa()
{
    int i,u,v,w,c;
    while(!que.empty()) que.pop();
    memset(dis,0x3f,sizeof(dis));
    memset(book,0,sizeof(book));
    memset(pre,-1,sizeof(pre));
    que.push(s);
    dis[s]=0,book[s]=1;
    while(!que.empty())
    {
        u=que.front();
        que.pop();
        book[u]=0;
        for(i=first[u];i!=-1;i=edge[i].next)
        {
            v=edge[i].v,w=edge[i].w,c=edge[i].c;
            if(w>0&&dis[v]>dis[u]+c)
            {
                dis[v]=dis[u]+c,pre[v]=i;
                if(!book[v])
                {
                    que.push(v);
                    book[v]=1;
                }
            }
        }
    }
    return dis[e];
}

int mcmf()
{
    int res,i,u,v,w,c,cost,minn;
    cost=0;
    while(1)
    {
        res=spfa();
        if(res==N) break;
        cost+=res;
        minn=N;
        for(i=pre[e];i!=-1;i=pre[v])
        {
            v=edge[i^1].v,w=edge[i].w;
            minn=min(minn,w);
        }
        for(i=pre[e];i!=-1;i=pre[v])
        {
            v=edge[i^1].v,c=edge[i].c;
            edge[i].w-=minn;
            edge[i^1].w+=minn;
        }
    }
    return cost;
}

int main()
{
    int i;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(n==0&&m==0) break;
        for(i=0;i<n;i++)
        {
            scanf("%s",mp[i]);
        }
        build();
        printf("%d\n",mcmf());
    }
    return 0;
}