HDU 2282 Chocolate （最小费用最大流）

HDU  2282 Chocolate （最小费用最大流）

#include <iostream>
#include <cstdio>
#include <queue>
#include <cstdlib>
using namespace std;

const int maxn=30000;
const int inf=200000000;
struct edge{
	int u,v,next,f,c;
	edge(int u0=0,int v0=0,int f0=0,int c0=0,int next0=0){
		u=u0,v=v0,f=f0,c=c0,next=next0;
	}	
}e[maxn*10];
int head[maxn*2],visited[maxn*2],path[maxn*2],dist[maxn*2];
int cnt,from,to,marked,maxflow,offflow,n,r,m;

void initial(){
	to=2*n+1;
	cnt=0;marked=1;
	maxflow=0;from=0;
	for(int i=0;i<=to;i++){
		head[i]=-1;
		visited[i]=0;
	}
}

void adde(int u,int v,int f,int c){
	e[cnt].u=u,e[cnt].v=v,e[cnt].f=f,e[cnt].c=c,e[cnt].next=head[u],head[u]=cnt++;
	e[cnt].u=v,e[cnt].v=u,e[cnt].f=0,e[cnt].c=-c,e[cnt].next=head[v],head[v]=cnt++;
}

void input(){
	int u0,c0;
	for(int i=1;i<=n;i++){
		adde(0,i,inf,0);
		adde(i+n,to,1,0);
	}
	for(int i=1;i<=n;i++){
		scanf("%d",&c0);
		adde(i,i+n,c0,0);
		adde(i+n,i-1<1?n+n:i-1+n,inf,1);
		adde(i+n,i+1>n?1+n:i+1+n,inf,1);
	}
}

void bfs(){
	 for(int i=0;i<=to;i++){
	 	dist[i]=inf;
	 	path[i]=-1;
	 }
	 dist[0]=0;
     queue <int> q;
     q.push(0);
     marked++;
     visited[0]=marked;
     while(!q.empty()){
         int s=q.front();
         q.pop();
         for(int i=head[s];i!=-1;i=e[i].next){
              int d=e[i].v;
              if(e[i].f>0 && dist[s]+e[i].c<dist[d]){
                 dist[d]=dist[s]+e[i].c;
                 path[d]=i;
                 if(visited[d]!=marked){
                 	visited[d]=marked;
                 	q.push(d);
                 }
              }
         }
         visited[s]=-1;
     }
}

void computing(){
	while(true){ 
     	bfs();
     	/*cout<<to;
     	for(int i=to;i!=from;i=e[path[i]].u){
     		cout<<"->"<<e[path[i]].u;
		}
		cout<<endl;*/
     	if(dist[to]>=inf) break;
		maxflow+=dist[to];
		for(int i=to;i!=from;i=e[path[i]].u){
     		e[path[i]].f-=1;
         	e[path[i]^1].f+=1;
		}
	}
    printf("%d\n",maxflow);
}

int main(){
	while(scanf("%d",&n)!=EOF){
		initial();
		input();
		computing();
	}
	return 0;
}