poj2195&&hdu1533 最小费用流

这题也可以用km做，我写的代码km比费用流快很多。

最小费用流:

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<queue>
#include<stdlib.h>
#define INF 1000000000
using namespace std;
const int maxn = ;
struct Set
{
    int x,y;
}mnum[*],hnum[*];
struct node
{
    int to;
    int v;
    int flag;
    int cost;
    int next;
}edge[maxn*maxn/];
char map[][];
int n,m,cou1,cou2,index,head[maxn],s,t,pre[maxn],fpre[maxn],N,dis[maxn];
int Get(int i,int j)
{
    return abs(mnum[i].x-hnum[j].x)+abs(mnum[i].y-hnum[j].y);
}
void add(int x,int y,int v,int cost)
{
    edge[index].to=y;
    edge[index].v=v;
    edge[index].cost=cost;
    edge[index].flag=index+;
    edge[index].next=head[x];
    head[x]=index++;
    edge[index].to=x;
    edge[index].v=;
    edge[index].cost=-cost;
    edge[index].flag=index-;
    edge[index].next=head[y];
    head[y]=index++;
}
void makemap()
{
    int i,j;
    cou1=cou2=;
    for(i=;i<n;i++)
    {
        for(j=;j<m;j++)
        {
            if(map[i][j]=='m')
            {
                mnum[++cou1].x=i;
                mnum[cou1].y=j;
            }
            else if(map[i][j]=='H')
            {
                hnum[++cou2].x=i;
                hnum[cou2].y=j;
            }
        }
    }
    index=;
    memset(head,-,sizeof(head));
    N=cou1+cou2+;
    s=;
    t=cou1+cou2+;
    for(i=;i<=cou1;i++)
        add(s,i,,);
    for(i=;i<=cou2;i++)
        add(i+cou1,t,,);
    for(i=;i<=cou1;i++)
    {
        for(j=;j<=cou2;j++)
        {
            add(i,j+cou1,,Get(i,j));
        }
    }
}
bool spfa(int s,int t)
{
    int vis[maxn];
    queue<int>q;
    memset(pre,-,sizeof(pre));
    memset(vis,,sizeof(vis));
    int i;
    for(i=;i<=N;i++)
        dis[i]=INF;
    vis[s]=;
    dis[s]=;
    pre[s]=;
    q.push(s);
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        vis[u]=;
        for(i=head[u];i!=-;i=edge[i].next)
        {
            if(edge[i].v&&dis[edge[i].to]>dis[u]+edge[i].cost)
            {
                dis[edge[i].to]=dis[u]+edge[i].cost;
                if(!vis[edge[i].to])
                {
                    vis[edge[i].to]=;
                    q.push(edge[i].to);
                }
                pre[edge[i].to]=u;
                fpre[edge[i].to]=i;
            }
        }
    }
    if(dis[t]>=INF)return false;
    return true;
}
int main()
{
    int i,j;
    while(~scanf("%d%d",&n,&m))
    {
        if(!n&&!m)break;
        for(i=;i<n;i++)
            scanf("%s",map[i]);
        makemap();
        int ans=;
        while(spfa(s,t))
        {
            int minflow=INF;
            for(i=t;i!=;i=pre[i])
            {
                if(minflow>edge[fpre[i]].v)
                    minflow=edge[fpre[i]].v;
            }
            ans+=minflow*dis[t];
            for(i=t;i!=;i=pre[i])
            {
                edge[fpre[i]].v-=minflow;
                edge[edge[fpre[i]].flag].v+=minflow;
            }
        }
        printf("%d\n",ans);
    }
}

km:

#include<stdio.h>
#include<string.h>
#include<algorithm>
#define INF 99999999
#define maxn 105
using namespace std;
struct node
{
    int x;
    int y;
}h[maxn],m[maxn];
char g[maxn][maxn];
int map[maxn][maxn],pr[maxn],pl[maxn],visr[maxn],visl[maxn],match[maxn],slack[maxn];
int col,row;
void init(int x)
{
    int i,j;
    for(i=;i<=x;i++)
        for(j=;j<=x;j++)
            if(i==j)map[i][j]=;
            else map[i][j]=INF;
}
int dfs(int u,int n)
{
    int i,j;
    visl[u]=;
    for(i=;i<n;i++)
    {
        if(!visr[i])
        {
            int val=pl[u]+pr[i]-map[u][i];
            if(val==)
            {
                visr[i]=;
                if(match[i]==-||dfs(match[i],n))
                {
                    match[i]=u;
                    return ;
                }
            }
            if(val>&&val<slack[i])
                slack[i]=val;
        }
    }
    return ;
}
int km(int n)
{
    int i,j;
    memset(pr,,sizeof(pr));
    memset(match,-,sizeof(match));
    for(i=;i<n;i++)
        pl[i]=INF;
    for(i=;i<n;i++)
    {
        for(j=;j<n;j++)
            slack[j]=INF;
        while()
        {
            memset(visr,,sizeof(visr));
            memset(visl,,sizeof(visl));
            if(dfs(i,n))break;
            int k=INF;
            for(j=;j<n;j++)
            {
                if(!visr[j]&&slack[j]<k)
                    k=slack[j];
            }
            for(j=;j<n;j++)
            {
                if(visl[j])
                    pl[j]-=k;
                if(visr[j])
                    pr[j]+=k;
            }
        }
    }
    int res=;
    for(i=;i<n;i++)
    {
        res+=map[match[i]][i];
    }
    return res;
}
int main()
{
    int i,j;
    while(scanf("%d%d",&row,&col)!=EOF)
    {
        if(row==&&col==)
            break;
        int count1=,count2=;
        for(i=;i<row;i++)
            scanf("%s",g[i]);
        for(i=;i<row;i++)
            for(j=;j<col;j++)
            {
                if(g[i][j]=='H')
                {
                    h[count1].x=i;h[count1++].y=j;
                }
                else if(g[i][j]=='m')
                {
                    m[count2].x=i;m[count2++].y=j;
                }
            }
        init(count1);
        for(i=;i<count1;i++)
            for(j=;j<count2;j++)
            {
                map[i][j]=-(abs(h[i].x-m[j].x)+abs(h[i].y-m[j].y));
            }
        printf("%d\n",-km(count1));
    }
}