【POJ2195】Going Home

题目

解析：

本质是个二分图带权匹配问题，建图后用费用流实现即可。

code：

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <queue>
#include <cstring>
using namespace std;

const int Maxn=205;
const int Maxm=10205;
const int inf=1e9;
int n,m,size,s,t,sum,tot1,tot2;
char c;
int dis[Maxn],v[Maxn],first[Maxn],tmp[Maxn];
struct shu{int to,next,l,c;}e[Maxm<<1];
struct zb{int x,y;}p1[Maxn],p2[Maxn];

inline int calc(int i,int j) {return abs(p1[i].x-p2[j].x)+abs(p1[i].y-p2[j].y);}

inline void add(int x,int y,int l,int c)
{
	e[++size].next=first[x],first[x]=size,e[size].to=y,e[size].l=l,e[size].c=c;
}

inline void init()
{
	tot1=tot2=0;
	for(int i=1;i<=n;i++)
	{
	  for(int j=1;j<=m;j++)
	  {
	     scanf("%c",&c);
	     if(c=='H') p2[++tot2].x=i,p2[tot2].y=j;
	     if(c=='m') p1[++tot1].x=i,p1[tot1].y=j;
	  }
	  scanf("\n");
	}
	t=2*tot1+1,sum=0,size=-1;
	for(int i=s;i<=t;i++) first[i]=-1;
	for(int i=1;i<=tot1;i++)
	{
	  add(s,i,1,0),add(i,s,0,0);
	  for(int j=1;j<=tot2;j++) add(i,tot1+j,1,calc(i,j)),add(tot1+j,i,0,-calc(i,j));
	}
	for(int i=1;i<=tot2;i++) add(tot1+i,t,1,0),add(t,tot1+i,0,0);
}

inline bool spfa()
{
	queue<int>q;
	for(int i=s;i<=t;i++) tmp[i]=first[i],dis[i]=inf;
	q.push(s),v[s]=1,dis[s]=0;
	while(!q.empty())
	{
	  int p=q.front();q.pop(),v[p]=0;
	  for(int u=first[p];~u;u=e[u].next)
	  {
	  	int to=e[u].to;
	  	if(dis[to]<=dis[p]+e[u].c || !e[u].l) continue;
	  	dis[to]=dis[p]+e[u].c;
	  	if(!v[to]) q.push(to),v[to]=1;
	  }
	}
	return dis[t]!=inf;
}

inline int dfs(int p,int flow)
{
	if(p==t) return flow;
	int s=0;v[p]=1;
	for(int &u=tmp[p];~u;u=e[u].next)
	{
	  int to=e[u].to;
	  if(v[to] || dis[to]!=dis[p]+e[u].c || !e[u].l) continue;
	  int minn=dfs(to,min(flow-s,e[u].l));
	  e[u].l-=minn,e[u^1].l+=minn,sum+=minn*e[u].c,s+=minn;
	  if(s==flow) break;
	}
	v[p]=0;
	return s;
}

inline void solve()
{
	while(spfa()) {while(dfs(s,inf));}
}

int main()
{
	while(1)
	{
	  scanf("%d%d\n",&n,&m);
	  if(!n) break;
	  init();
	  solve();
	  cout<<sum<<"\n";
	}
	return 0;
}

标签：code,const,int,Going,Maxn,Maxm,Home,include,POJ2195
来源： https://www.cnblogs.com/Tarjan-Zeng/p/15083831.html