POJ-2195-Going Home

POJ-2195-Going Home

http://poj.org/problem?id=2195

最小費用最大流，假想一個源點，一個匯點

代碼模仿網上的寫的，還要再好好研究哇

#include<stdio.h>
#include<string.h>
#include<math.h>
#define maxn 300
#define INF 0x7fffffff
int min(int x,int y)
{
	return x<y?x:y;
}
struct node  
{
	int x;
	int y;
}h[maxn],man[maxn];
int map[maxn][maxn],vis[maxn],cap[maxn][maxn],dis[maxn];
int que[maxn],pre[maxn];
int num,ans;
int SPFA() 
{
	int i,k;
	int head,tail;
	memset(vis,0,sizeof(vis));
	for(i=0;i<=num;i++)
	dis[i]=INF;
	dis[0]=0;
	vis[0]=1;
	head=tail=0;
	que[0]=0;
	tail++;
	while(head<tail)
	{
       k=que[head];
	   vis[k]=0;
	   for(i=0;i<=num;i++)
	   {
		   if(cap[k][i]&&dis[i]>dis[k]+map[k][i])
		   {
			   dis[i]=dis[k]+map[k][i];
			   pre[i]=k;
			   if(!vis[i])
			   {
				   vis[i]=1;
				   que[tail++]=i;
			   }
		   }
	   }
	   head++;
	}
	if(dis[num]<INF)
	return 1;
	return 0;
}
void end()
{
	int i,sum=INF;
	for(i=num;i!=0;i=pre[i])
	sum=min(sum,cap[pre[i]][i]);
	for(i=num;i!=0;i=pre[i])
	{
		cap[pre[i]][i]-=sum;
		cap[i][pre[i]]+=sum;
		ans+=map[pre[i]][i]*sum;
	}
}
int main()
{
	int hnum,mnum,n,m,i,j;
	char c;
	while(scanf("%d%d",&n,&m)!=EOF,n||m)
	{
		hnum=0;
		mnum=0;
		getchar();
		for(i=0;i<n;i++)
		{
			for(j=0;j<m;j++)
			{
				scanf("%c",&c);
				if(c=='H')
				{
					h[++hnum].x=i;
					h[hnum].y=j;
				}
				else if(c=='m')
				{
					man[++mnum].x=i;
					man[mnum].y=j;
				}
			}
			getchar();
		}
		memset(cap,0,sizeof(cap));
		memset(map,0,sizeof(map));
		for(i=1;i<=mnum;i++)
		{
			for(j=1;j<=hnum;j++)
			{
				cap[i][j+mnum]=1;
				map[i][j+mnum]=abs(man[i].x-h[j].x)+abs(man[i].y-h[j].y);
				map[j+mnum][i]=-(map[i][j+mnum]);
			}
		}
		num=mnum+hnum+1;
		for(i=1;i<=mnum;i++)
		{
			map[0][i]=map[i][0]=0;
			cap[0][i]=1;
		}
		for(i=mnum+1;i<num;i++)
		{
			map[i][num]=map[num][i]=0;
			cap[i][num]=1;
		}
		ans=0;
		while(SPFA())
		end();
		printf("%d\n",ans);
	}
    return 0;
}