poj 2195 Going Home (费用流)

来源：互联网发布：java初级中级高级编辑：程序博客网时间：2024/06/05 22:16
水题，直接搞。
#include<iostream>#include<math.h>#include<stdio.h>#include<algorithm>#include<string.h>#include<string>#include<vector>#include<queue>#include<map>#include<set>#define B(x) (1<<(x))using namespace std;void cmax(int& a,int b){ if(b>a)a=b; }void cmin(int& a,int b){ if(b<a)a=b; }typedef long long ll;const int oo=0x3f3f3f3f;const ll OO=1LL<<61;const int MOD=1000007;const int maxn=302020;const int maxm=1602020;struct EDGE{    int v,next,c,f,cost;}E[maxm<<1];int head[maxn],tol;int dis[maxn],pre[maxn];int vis[maxn];void Init(){    memset(head,-1,sizeof head);    tol=0;}void add_edge(int u,int v,int f,int cost){    E[tol].v=v;    E[tol].c=f;    E[tol].f=0;    E[tol].cost=cost;    E[tol].next=head[u];    head[u]=tol++;    E[tol].v=u;    E[tol].c=0;    E[tol].f=0;    E[tol].cost=-cost;    E[tol].next=head[v];    head[v]=tol++;}bool Spfa(int s,int t){    for(int i=0;i<=t;i++){        pre[i]=-1;        dis[i]=oo;        vis[i]=0;    }    dis[s]=0;    vis[s]=1;    queue<int>q;    q.push(s);    while(!q.empty()){        int u=q.front();q.pop();        vis[u]=0;        for(int i=head[u];i!=-1;i=E[i].next){            int v=E[i].v;            if(E[i].c>E[i].f&&dis[v]>dis[u]+E[i].cost){                dis[v]=dis[u]+E[i].cost;                pre[v]=i;                if(!vis[v]){                    vis[v]=1;                    q.push(v);                }            }        }    }    return dis[t]!=oo;}int min_cost_maxflow(int s,int t,int& cost){    int flow=0;    cost=0;    while(Spfa(s,t)){        int Min=oo;        for(int i=pre[t];i!=-1;i=pre[E[i^1].v]){            if(Min>E[i].c-E[i].f)                Min=E[i].c-E[i].f;        }        for(int i=pre[t];i!=-1;i=pre[E[i^1].v]){            E[i].f+=Min;            E[i^1].f-=Min;            cost+=Min*E[i].cost;        }        flow+=Min;    }    return flow;}char maze[205][205];struct Node{    int x,y;    Node(){}    Node(int x_,int y_){ x=x_; y=y_; }}a[maxn],b[maxn];int Dis(Node n1,Node n2){    return abs(n1.x-n2.x)+abs(n1.y-n2.y);}int main(){    //freopen("G:\\read.txt","r",stdin);    int n,m,s,t;    while(scanf("%d%d",&n,&m)!=EOF){        if(n==0&&m==0)break;        for(int i=0;i<n;i++)scanf("%s",maze[i]);        int n1=0,n2=0;        for(int i=0;i<n;i++){            for(int j=0;j<m;j++){                if(maze[i][j]=='H')b[n2++]=Node(i,j);                if(maze[i][j]=='m')a[n1++]=Node(i,j);            }        }        Init();        s=n1+n2+1;        t=s+1;        for(int i=0;i<n1;i++){            for(int j=0;j<n2;j++){               add_edge(i,j+n1,1,Dis(a[i],b[j]));            }        }        for(int i=0;i<n1;i++)add_edge(s,i,1,0);        for(int i=0;i<n2;i++)add_edge(i+n1,t,1,0);        int cost;        min_cost_maxflow(s,t,cost);        printf("%d\n",cost);    }    return 0;}/**/
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