POJ 2195 一人一房 最小费用流 建图 水题

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <queue>
#include <map>
#include <algorithm>
#include <set>
using namespace std;
#define MM(a,b) memset(a,b,sizeof(a))
typedef long long ll;
typedef unsigned long long ULL;
const int mod = 1000000007;
const double eps = 1e-10;
const int inf = 0x3f3f3f3f;
const int big=50000;
int max(int a,int b) {return a>b?a:b;};
int min(int a,int b) {return a<b?a:b;};
const int N = 70;
const int M=10000+100;
struct edge{
   int to,cap,cost,rev;
};

vector<edge> G[1005];
int dist[1005],inq[1005],prev[1005],prel[1005];
struct Point{
   int x,y;
};

int n,m,x,y,c,cnth,cntm;
Point house[105],men[105];

void add_edge(int u,int v,int cap,int cost)
{
    G[u].push_back(edge{v,cap,cost,G[v].size()});
    G[v].push_back(edge{u,0,-cost,G[u].size()-1});
}

int mincost(int s,int t,int f)
{
    int ans=0;
    while(f>0)
    {
      memset(dist,inf,sizeof(dist));
      memset(inq,0,sizeof(inq));
      dist[s]=0;
      queue<int> q;
      q.push(s);
      inq[s]=1;
      MM(prev,-1);
      while(!q.empty())
      {
          int u=q.front();
          q.pop();inq[u]=0;
          for(int j=0;j<G[u].size();j++)
            {
                edge &e=G[u][j];
                if(e.cap>0&&dist[e.to]>dist[u]+e.cost)
                   {
                       dist[e.to]=dist[u]+e.cost;
                       prev[e.to]=u;
                       prel[e.to]=j;
                       if(!inq[e.to])
                       {
                           q.push(e.to);
                           inq[e.to]=1;
                       }
                   }
            }
       }
       for(int i=t;i>s;)
       {
           int f=prev[i];
           if(f==-1) return -1;
           int j=prel[i];
           G[f][j].cap-=1;
           G[i][G[f][j].rev].cap+=1;
           ans+=G[f][j].cost;
           i=prev[i];
       }
       f-=1;
    }
    return ans;
}

void build()
{
    for(int i=0;i<=cnth+cntm+1;i++) G[i].clear();
    for(int i=1;i<=cntm;i++)
          add_edge(0,i,1,0);
    for(int i=1;i<=cnth;i++)
          add_edge(cntm+i,cntm+cnth+1,1,0);
    for(int i=1;i<=cntm;i++)
          for(int j=1;j<=cnth;j++)
        {
          int dis=abs(house[j].x-men[i].x)+abs(house[j].y-men[i].y);
          add_edge(i,j+cntm,1,dis);
        }
}

char s[105][105];
int main()
{
    int n,m;
    while(~scanf("%d %d",&n,&m)&&(n||m))
    {
        cnth=cntm=0;
        for(int i=1;i<=n;i++)
           {
               scanf("%s",s[i]);
               for(int j=0;j<m;j++)
                   if(s[i][j]==‘H‘)
                      house[++cnth]=(Point){i,j+1};
                   else if(s[i][j]==‘m‘)
                      men[++cntm]=(Point){i,j+1};
           }
        build();
        printf("%d\n",mincost(0,cnth+cntm+1,cnth));
    }
    return 0;
}