POJ---1149 PIGS[dinic()最大流]
2012-09-08 00:52
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PIGS
Description
Mirko works on a pig farm that consists of M locked pig-houses and Mirko can't unlock any pighouse because he doesn't have the keys. Customers come to the farm one after another. Each of them has keys to some pig-houses and wants to buy a certain number of pigs.
All data concerning customers planning to visit the farm on that particular day are available to Mirko early in the morning so that he can make a sales-plan in order to maximize the number of pigs sold.
More precisely, the procedure is as following: the customer arrives, opens all pig-houses to which he has the key, Mirko sells a certain number of pigs from all the unlocked pig-houses to him, and, if Mirko wants, he can redistribute the remaining pigs across the unlocked pig-houses.
An unlimited number of pigs can be placed in every pig-house.
Write a program that will find the maximum number of pigs that he can sell on that day.
Input
The first line of input contains two integers M and N, 1 <= M <= 1000, 1 <= N <= 100, number of pighouses and number of customers. Pig houses are numbered from 1 to M and customers are numbered from 1 to N.
The next line contains M integeres, for each pig-house initial number of pigs. The number of pigs in each pig-house is greater or equal to 0 and less or equal to 1000.
The next N lines contains records about the customers in the following form ( record about the i-th customer is written in the (i+2)-th line):
A K1 K2 ... KA B It means that this customer has key to the pig-houses marked with the numbers K1, K2, ..., KA (sorted nondecreasingly ) and that he wants to buy B pigs. Numbers A and B can be equal to 0.
Output
The first and only line of the output should contain the number of sold pigs.
Sample Input
Sample Output
Source
Croatia OI 2002 Final Exam - First day
这题主要是构图比较难,这题以人为节点,如果有公共节点的人就作为前驱
code:
Time Limit: 1000MS | Memory Limit: 10000K | |
Total Submissions: 12578 | Accepted: 5560 |
Mirko works on a pig farm that consists of M locked pig-houses and Mirko can't unlock any pighouse because he doesn't have the keys. Customers come to the farm one after another. Each of them has keys to some pig-houses and wants to buy a certain number of pigs.
All data concerning customers planning to visit the farm on that particular day are available to Mirko early in the morning so that he can make a sales-plan in order to maximize the number of pigs sold.
More precisely, the procedure is as following: the customer arrives, opens all pig-houses to which he has the key, Mirko sells a certain number of pigs from all the unlocked pig-houses to him, and, if Mirko wants, he can redistribute the remaining pigs across the unlocked pig-houses.
An unlimited number of pigs can be placed in every pig-house.
Write a program that will find the maximum number of pigs that he can sell on that day.
Input
The first line of input contains two integers M and N, 1 <= M <= 1000, 1 <= N <= 100, number of pighouses and number of customers. Pig houses are numbered from 1 to M and customers are numbered from 1 to N.
The next line contains M integeres, for each pig-house initial number of pigs. The number of pigs in each pig-house is greater or equal to 0 and less or equal to 1000.
The next N lines contains records about the customers in the following form ( record about the i-th customer is written in the (i+2)-th line):
A K1 K2 ... KA B It means that this customer has key to the pig-houses marked with the numbers K1, K2, ..., KA (sorted nondecreasingly ) and that he wants to buy B pigs. Numbers A and B can be equal to 0.
Output
The first and only line of the output should contain the number of sold pigs.
Sample Input
3 3 3 1 10 2 1 2 2 2 1 3 3 1 2 6
Sample Output
7
Source
Croatia OI 2002 Final Exam - First day
这题主要是构图比较难,这题以人为节点,如果有公共节点的人就作为前驱
code:
#include<iostream> using namespace std; #define MAXN 110 #define inf 0x7fffffff int n,m; int cnt[1010]; int pre[1010]; int dis[1010]; int edgenum; typedef struct edge { int from,to,cap; int next; }Edge; Edge edge[MAXN*10]; int head[MAXN]; void addedge(int a,int b,int c) { edge[edgenum].from=a,edge[edgenum].to=b,edge[edgenum].cap=c,edge[edgenum].next=head[a],head[a]=edgenum++; edge[edgenum].from=b,edge[edgenum].to=a,edge[edgenum].cap=0,edge[edgenum].next=head[b],head[b]=edgenum++; } int dinic(int st,int et) { int sta[1010]; int que[1010]; int ans=0; while(true) { memset(dis,-1,sizeof(dis)); int front=0,tail=0; int u,v; dis[st]=0; que[tail++]=st; while(front<tail) { v=que[front++]; for(int i=head[v];i!=-1;i=edge[i].next) { u=edge[i].to; if(dis[u]==-1&&edge[i].cap>0) { dis[u]=dis[v]+1; que[tail++]=u; if(u==et) { front=tail; break; } } } } if(dis[et]==-1) break; int t=0; int s=st; while(true) { if(s!=et) { int i; for(i=head[s];i!=-1;i=edge[i].next) if(edge[i].cap>0&&dis[edge[i].from]+1==dis[edge[i].to]) break; if(i!=-1) { sta[t++]=i; s=edge[i].to; } else { if(t==0) break; dis[edge[sta[--t]].to]=-1; s=edge[sta[t]].from; } } else { int mindis=inf; int tag; for(int i=0;i<t;i++) if(mindis>edge[sta[i]].cap) { mindis=edge[sta[i]].cap; tag=i; } ans+=mindis; for(int i=0;i<t;i++) { edge[sta[i]].cap-=mindis; edge[sta[i]^1].cap+=mindis; } s=edge[sta[tag]].from; t=tag; } } } return ans; } int main() { int i,j; int vst[1010]; edgenum=0; memset(vst,0,sizeof(vst)); memset(head,-1,sizeof(head)); memset(pre,0,sizeof(pre)); scanf("%d%d",&m,&n); //m:猪栏数量;n:人数 int s=0,t=n+1; for(int i=1;i<=m;i++) scanf("%d",&cnt[i]); for(i=1;i<=n;i++) { int count,a,cap; int ans=0; scanf("%d",&count); for(j=0;j<count;j++) { scanf("%d",&a); if(!vst[a]) { ans+=cnt[a]; vst[a]=true; pre[a]=i; } else { addedge(pre[a],i,inf); } } if(ans) addedge(s,i,ans); scanf("%d",&cap); addedge(i,t,cap); } printf("%d\n",dinic(s,t)); return 0; }
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