http://acm.hdu.edu.cn/showproblem.php?pid=4940
Destroy Transportation system
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 298 Accepted Submission(s): 184
Problem Description
Tom is a commander, his task is destroying his enemy’s transportation system.
Let’s represent his enemy’s transportation system as a simple directed graph G with n nodes and m edges. Each node is a city and each directed edge is a directed road. Each edge from node u to node v is associated with two values D and B, D is the cost to destroy/remove such edge, B is the cost to build an undirected edge between u and v.
His enemy can deliver supplies from city u to city v if and only if there is a directed path from u to v. At first they can deliver supplies from any city to any other cities. So the graph is a strongly-connected graph.
He will choose a non-empty proper subset of cities, let’s denote this set as S. Let’s denote the complement set of S as T. He will command his soldiers to destroy all the edges (u, v) that u belongs to set S and v belongs to set T.
To destroy an edge, he must pay the related cost D. The total cost he will pay is X. You can use this formula to calculate X:
![](http://acm.hdu.edu.cn/data/images/C508-1006-1.jpg)
After that, all the edges from S to T are destroyed. In order to deliver huge number of supplies from S to T, his enemy will change all the remained directed edges (u, v) that u belongs to set T and v belongs to set S into undirected edges. (Surely, those edges exist because the original graph is strongly-connected)
To change an edge, they must remove the original directed edge at first, whose cost is D, then they have to build a new undirected edge, whose cost is B. The total cost they will pay is Y. You can use this formula to calculate Y:
![](http://acm.hdu.edu.cn/data/images/C508-1006-2.jpg)
At last, if Y>=X, Tom will achieve his goal. But Tom is so lazy that he is unwilling to take a cup of time to choose a set S to make Y>=X, he hope to choose set S randomly! So he asks you if there is a set S, such that Y<X. If such set exists, he will feel unhappy, because he must choose set S carefully, otherwise he will become very happy.
Let’s represent his enemy’s transportation system as a simple directed graph G with n nodes and m edges. Each node is a city and each directed edge is a directed road. Each edge from node u to node v is associated with two values D and B, D is the cost to destroy/remove such edge, B is the cost to build an undirected edge between u and v.
His enemy can deliver supplies from city u to city v if and only if there is a directed path from u to v. At first they can deliver supplies from any city to any other cities. So the graph is a strongly-connected graph.
He will choose a non-empty proper subset of cities, let’s denote this set as S. Let’s denote the complement set of S as T. He will command his soldiers to destroy all the edges (u, v) that u belongs to set S and v belongs to set T.
To destroy an edge, he must pay the related cost D. The total cost he will pay is X. You can use this formula to calculate X:
![](http://acm.hdu.edu.cn/data/images/C508-1006-1.jpg)
After that, all the edges from S to T are destroyed. In order to deliver huge number of supplies from S to T, his enemy will change all the remained directed edges (u, v) that u belongs to set T and v belongs to set S into undirected edges. (Surely, those edges exist because the original graph is strongly-connected)
To change an edge, they must remove the original directed edge at first, whose cost is D, then they have to build a new undirected edge, whose cost is B. The total cost they will pay is Y. You can use this formula to calculate Y:
![](http://acm.hdu.edu.cn/data/images/C508-1006-2.jpg)
At last, if Y>=X, Tom will achieve his goal. But Tom is so lazy that he is unwilling to take a cup of time to choose a set S to make Y>=X, he hope to choose set S randomly! So he asks you if there is a set S, such that Y<X. If such set exists, he will feel unhappy, because he must choose set S carefully, otherwise he will become very happy.
Input
There are multiply test cases.
The first line contains an integer T(T<=200), indicates the number of cases.
For each test case, the first line has two numbers n and m.
Next m lines describe each edge. Each line has four numbers u, v, D, B.
(2=<n<=200, 2=<m<=5000, 1=<u, v<=n, 0=<D, B<=100000)
The meaning of all characters are described above. It is guaranteed that the input graph is strongly-connected.
The first line contains an integer T(T<=200), indicates the number of cases.
For each test case, the first line has two numbers n and m.
Next m lines describe each edge. Each line has four numbers u, v, D, B.
(2=<n<=200, 2=<m<=5000, 1=<u, v<=n, 0=<D, B<=100000)
The meaning of all characters are described above. It is guaranteed that the input graph is strongly-connected.
Output
For each case, output "Case #X: " first, X is the case number starting from 1.If such set doesn’t exist, print “happy”, else print “unhappy”.
Sample Input
2 3 3 1 2 2 2 2 3 2 2 3 1 2 2 3 3 1 2 10 2 2 3 2 2 3 1 2 2
Sample Output
Case #1: happy Case #2: unhappyHintIn first sample, for any set S, X=2, Y=4. In second sample. S= {1}, T= {2, 3}, X=10, Y=4.
题意:给出一个有向强连通图,每条边有两个值分别是破坏该边的代价和把该边建成无向边的代价(建立无向边的前提是删除该边)问是否存在一个集合S,和一个集合的补集T,破坏所有S集合到T集合的边代价和是X,然后修复T到S的边为无向边代价和是Y,满足Y<X;满足输出unhappy,否则输出happy;
分析:首先可以把每条边的权值做一下变换,即破坏有向边的权值A=d,和建立无向边的权值B=b+d;
官方题解:
程序:
#include"string.h" #include"stdio.h" #include"iostream" #include"queue" #define inf 100000000 #include"math.h" #define M 333 #define eps 1e-5 using namespace std; struct node { int u,v,w,c,next; }edge[40009]; int t,head[M],dis[M],work[M]; void init() { t=0; memset(head,-1,sizeof(head)); } void add(int u,int v,int w,int c) { edge[t].u=u; edge[t].v=v; edge[t].w=w; edge[t].c=c; edge[t].next=head[u]; head[u]=t++; edge[t].u=v; edge[t].v=u; edge[t].w=0; edge[t].c=c; edge[t].next=head[v]; head[v]=t++; } int bfs(int start,int endl) { queue<int>q; memset(dis,-1,sizeof(dis)); dis[start]=0; q.push(start); while(!q.empty()) { int u=q.front(); q.pop(); for(int i=head[u];i!=-1;i=edge[i].next) { int v=edge[i].v; if(edge[i].w&&dis[v]==-1) { dis[v]=dis[u]+1; q.push(v); if(v==endl) return 1; } } } return 0; } int dfs(int u,int a,int T) { if(u==T) return a; for(int &i=work[u];i!=-1;i=edge[i].next) { int v=edge[i].v; if(edge[i].w&&dis[v]==dis[u]+1) { int tt=dfs(v,min(edge[i].w,a),T); if(tt) { edge[i].w-=tt; edge[i^1].w+=tt; return tt; } } } return 0; } int Dinic(int S,int T) { int ans=0; while(bfs(S,T)) { memcpy(work,head,sizeof(head)); while(int tt=dfs(S,inf,T)) ans+=tt; } return ans; } int main() { int T,kk=1; cin>>T; while(T--) { int n,m; scanf("%d%d",&n,&m); init(); int st=0; int sd=n+1; int sum=0; while(m--) { int a,b,c,d; scanf("%d%d%d%d",&a,&b,&c,&d); sum+=c; add(a,b,d,c+d); add(a,sd,c,c); add(st,b,c,c); } int ans=Dinic(st,sd); printf("Case #%d: ",kk++); if(sum!=ans) { printf("unhappy "); } else printf("happy "); } return 0; }