网络流(最大流):POJ 1149 PIGS
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PIGS
Time Limit: 1000ms
Memory Limit: 10000KB
This problem will be judged on PKU. 64-bit integer(整数) IO format: %lld Java class name: Main
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(关于) 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(取…最大值) the number of pigs sold.
More precisely(精确地), the procedure(程序) is as following: the customer arives, 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(重新分配) 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.
All data concerning(关于) 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(取…最大值) the number of pigs sold.
More precisely(精确地), the procedure(程序) is as following: the customer arives, 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(重新分配) 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(投入) contains two integers(整数)
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(不减少的) ) and that he wants to buy B pigs. Numbers A and B can be equal to 0.
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(不减少的) ) 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(输出) 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
建模题,这里需要注意对空间的优化。
1 #include <iostream> 2 #include <cstring> 3 #include <cstdio> 4 #include <queue> 5 6 using namespace std; 7 const int INF=2147483647; 8 const int maxn=1010,maxm=4010; 9 int cnt,fir[maxn],nxt[maxm],cap[maxm],to[maxm],dis[maxn],gap[maxn],path[maxn],used[maxn]; 10 11 void addedge(int a,int b,int c) 12 { 13 nxt[++cnt]=fir[a]; 14 to[cnt]=b; 15 cap[cnt]=c; 16 fir[a]=cnt; 17 } 18 19 bool BFS(int S,int T) 20 { 21 memset(dis,0,sizeof(dis)); 22 dis[T]=1; 23 queue<int>q;q.push(T); 24 while(!q.empty()) 25 { 26 int node=q.front();q.pop(); 27 for(int i=fir[node];i;i=nxt[i]) 28 { 29 if(dis[to[i]])continue; 30 dis[to[i]]=dis[node]+1; 31 q.push(to[i]); 32 } 33 } 34 return dis[S]; 35 } 36 int fron[maxn]; 37 int ISAP(int S,int T) 38 { 39 if(!BFS(S,T)) 40 return 0; 41 for(int i=1;i<=T;i++)++gap[dis[i]]; 42 int p=S,ret=0; 43 memcpy(fron,fir,sizeof(fir)); 44 while(dis[S]<=T) 45 { 46 if(p==T){ 47 int f=INF; 48 while(p!=S){ 49 f=min(f,cap[path[p]]); 50 p=to[path[p]^1]; 51 } 52 p=T;ret+=f; 53 while(p!=S){ 54 cap[path[p]]-=f; 55 cap[path[p]^1]+=f; 56 p=to[path[p]^1]; 57 } 58 } 59 int &ii=fron[p]; 60 for(;ii;ii=nxt[ii]){ 61 if(!cap[ii]||dis[to[ii]]+1!=dis[p]) 62 continue; 63 else 64 break; 65 } 66 if(ii){ 67 p=to[ii]; 68 path[p]=ii; 69 } 70 else{ 71 if(--gap[dis[p]]==0)break; 72 int minn=T+1; 73 for(int i=fir[p];i;i=nxt[i]) 74 if(cap[i]) 75 minn=min(minn,dis[to[i]]); 76 gap[dis[p]=minn+1]++; 77 fron[p]=fir[p]; 78 if(p!=S) 79 p=to[path[p]^1]; 80 } 81 } 82 return ret; 83 } 84 85 void Init() 86 { 87 memset(fir,0,sizeof(fir)); 88 memset(used,0,sizeof(used)); 89 cnt=1; 90 } 91 int main() 92 { 93 int n,m,num,k,need; 94 while(~scanf("%d%d",&m,&n)) 95 { 96 Init(); 97 for(int i=1;i<=m;i++){ 98 scanf("%d",&num); 99 addedge(0,i,num); 100 addedge(i,0,0); 101 } 102 for(int i=m+1;i<=m+n;i++){ 103 scanf("%d",&k); 104 while(k--){ 105 scanf("%d",&num); 106 if(used[num]){ 107 addedge(used[num],i,INF); 108 addedge(i,used[num],0); 109 } 110 else{ 111 used[num]=i; 112 addedge(num,i,INF); 113 addedge(i,num,0); 114 } 115 116 } 117 scanf("%d",&need); 118 addedge(i,n+m+1,need); 119 addedge(n+m+1,i,0); 120 } 121 printf("%d\n",ISAP(0,n+m+1)); 122 } 123 return 0; 124 }
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