博客
关于我
强烈建议你试试无所不能的chatGPT,快点击我
Power Network (最大流增广路算法模板题)
阅读量:4485 次
发布时间:2019-06-08

本文共 4995 字,大约阅读时间需要 16 分钟。

Time Limit: 2000MS   Memory Limit: 32768K
Total Submissions: 20754   Accepted: 10872

Description

A power network consists of nodes (power stations, consumers and dispatchers) connected by power transport lines. A node u may be supplied with an amount s(u) >= 0 of power, may produce an amount 0 <= p(u) <= p
max(u) of power, may consume an amount 0 <= c(u) <= min(s(u),c
max(u)) of power, and may deliver an amount d(u)=s(u)+p(u)-c(u) of power. The following restrictions apply: c(u)=0 for any power station, p(u)=0 for any consumer, and p(u)=c(u)=0 for any dispatcher. There is at most one power transport line (u,v) from a node u to a node v in the net; it transports an amount 0 <= l(u,v) <= l
max(u,v) of power delivered by u to v. Let Con=Σ
uc(u) be the power consumed in the net. The problem is to compute the maximum value of Con. 
An example is in figure 1. The label x/y of power station u shows that p(u)=x and p
max(u)=y. The label x/y of consumer u shows that c(u)=x and c
max(u)=y. The label x/y of power transport line (u,v) shows that l(u,v)=x and l
max(u,v)=y. The power consumed is Con=6. Notice that there are other possible states of the network but the value of Con cannot exceed 6. 

Input

There are several data sets in the input. Each data set encodes a power network. It starts with four integers: 0 <= n <= 100 (nodes), 0 <= np <= n (power stations), 0 <= nc <= n (consumers), and 0 <= m <= n^2 (power transport lines). Follow m data triplets (u,v)z, where u and v are node identifiers (starting from 0) and 0 <= z <= 1000 is the value of l
max(u,v). Follow np doublets (u)z, where u is the identifier of a power station and 0 <= z <= 10000 is the value of p
max(u). The data set ends with nc doublets (u)z, where u is the identifier of a consumer and 0 <= z <= 10000 is the value of c
max(u). All input numbers are integers. Except the (u,v)z triplets and the (u)z doublets, which do not contain white spaces, white spaces can occur freely in input. Input data terminate with an end of file and are correct.

Output

For each data set from the input, the program prints on the standard output the maximum amount of power that can be consumed in the corresponding network. Each result has an integral value and is printed from the beginning of a separate line.

Sample Input

2 1 1 2 (0,1)20 (1,0)10 (0)15 (1)207 2 3 13 (0,0)1 (0,1)2 (0,2)5 (1,0)1 (1,2)8 (2,3)1 (2,4)7         (3,5)2 (3,6)5 (4,2)7 (4,3)5 (4,5)1 (6,0)5         (0)5 (1)2 (3)2 (4)1 (5)4

Sample Output

156

Hint

The sample input contains two data sets. The first data set encodes a network with 2 nodes, power station 0 with pmax(0)=15 and consumer 1 with cmax(1)=20, and 2 power transport lines with lmax(0,1)=20 and lmax(1,0)=10. The maximum value of Con is 15. The second data set encodes the network from figure 1.
1 #include
2 #include
3 #include
4 using namespace std; 5 6 const int MAX = 150; 7 const int INF = 0x3f3f3f3f; 8 int n,np,nc,m,mf,s,t; 9 int cap[MAX][MAX],flow[MAX][MAX],a[MAX];10 int pre[MAX];11 char str[20];12 queue
que;13 void maxflow()14 {15 memset(flow,0,sizeof(flow));//初始化,所有的边的流量初始为0;16 mf = 0;//记录最大流17 for(;;)18 {19 memset(a,0,sizeof(a));//s到每个节点路径上的最小残量20 a[s] = INF;21 que.push(s);22 //bfs找增广路23 while(!que.empty())24 {25 int u = que.front();26 que.pop();27 for(int v = 0; v <= n+1; v++)28 {29 if(!a[v] && cap[u][v] > flow[u][v])//找到新的节点v30 {31 pre[v] = u;//记录前驱并加入队列32 que.push(v);33 if(a[u] < cap[u][v]-flow[u][v])34 a[v] = a[u];35 else a[v] = cap[u][v]-flow[u][v];//s到v路径上的最小残量36 }37 }38 }39 if(a[t] == 0) break;//找不到最小残量,当前流已经是最大流;40 for(int u = t; u!= s;u = pre[u])//从汇点往回走41 {42 flow[pre[u]][u] += a[t];//更新正向流量43 flow[u][pre[u]] -= a[t];//更新反向流量44 }45 mf += a[t];//更新从s流出的总流量46 }47 }48 49 50 int main()51 {52 int u,v,z;53 while(~scanf("%d %d %d %d",&n,&np,&nc,&m))54 {55 memset(cap,0,sizeof(cap));56 while(m--)57 {58 scanf("%s",str);59 sscanf(str,"(%d,%d)%d",&u,&v,&z);60 cap[u][v] = z;61 }62 63 while(np--)//有多个起点64 {65 scanf("%s",str);66 sscanf(str,"(%d)%d",&v,&z);67 cap[n][v] = z;//将多个起点连接到一个新的顶点作为起点;68 }69 70 while(nc--)//有多个终点71 {72 scanf("%s",str);73 sscanf(str,"(%d)%d",&u,&z);74 cap[u][n+1] = z;//将多个终点连接到一个新的终点作为终点;75 }76 s = n;77 t = n+1;78 maxflow();79 printf("%d\n",mf);80 }81 return 0;82 }
View Code

 

转载于:https://www.cnblogs.com/LK1994/p/3253233.html

你可能感兴趣的文章
js弹出框
查看>>
(转) sphinx 高亮显示搜索词
查看>>
HTTP协议的URI及各种方法
查看>>
用最简单话概括SSH三框架
查看>>
JSP
查看>>
Time, Clocks, and the Ordering of Events in a Distributed System
查看>>
C#成员基础
查看>>
字符设备 register_chrdev_region()、alloc_chrdev_region() 和 register_chrdev()
查看>>
为Azure Web Site 添加ADFS验证支持之二 在代码里使用ADFS
查看>>
day1--计算机基础1
查看>>
phpStudy
查看>>
编程珠玑——第一章习题
查看>>
mapper.xml文件中标签不显示问题
查看>>
JavaScript的事件
查看>>
ios中实现对UItextField,UITextView等输入框的字数限制
查看>>
PAT Basic 1008
查看>>
[Information Theory] L1: Introduction to Information Theory
查看>>
相册分类列表页
查看>>
各浏览器的鼠标位置测试
查看>>
[BZOJ1070][SCOI2007]修车(最小费用最大流)
查看>>