poj2391 Ombrophobic Bovines 拆点连边要注意

  1 #include<iostream>
  2 #include<vector>
  3 #include<string.h>
  4 #include<queue>
  5 #include<cstdio>
  6 using namespace std;
  7 #define INF 10000000
  8 #define maxn 820
  9 
 10 struct E{int from;int to;int c;int f;};
 11 vector <int> g[maxn];
 12 vector<E> edge;
 13 int d[maxn],vis[maxn],cur[maxn],num[maxn],p[220],n,tot;
 14 
 15 int dis[202][202],nz[202],you[202];
 16 
 17 
 18 void add(int from,int to,int c)
 19 {
 20     E temp1,temp2;
 21     temp1.from =from; temp1.to=to; temp1.c=c;temp1.f=0;
 22     temp2.from =to; temp2.to=from; temp2.c=0;temp2.f=0;
 23     edge.push_back (temp1);
 24     edge.push_back (temp2);
 25     int m=edge.size ();
 26     g[from].push_back (m-2);
 27     g[to].push_back (m-1);
 28 }
 29 
 30 void bfs(int s,int t)
 31 {
 32     int i;
 33     queue<int > q;
 34     q.push (t);
 35     d[t]=0;
 36     memset(vis,0,sizeof(vis));
 37     vis[t]=1;
 38     while(!q.empty ())
 39     {
 40         int t=q.front ();q.pop ();
 41         for(i=0;i<g[t].size ();i++)
 42         {
 43            E e;e=edge[g[t][i]];
 44            if(!vis[e.to])
 45            {
 46                q.push (e.to);
 47                vis[e.to]=1;
 48                d[e.to]=d[t]+1;
 49            }
 50         }
 51     }
 52 }
 53 
 54 int zg(int s,int t)
 55 {
 56     int x=t,a=INF;
 57     while(x!=s)
 58     {
 59         //printf("x   %d\n",x);
 60         E e=edge[p[x]];
 61         if(a>e.c-e.f)
 62             a=e.c-e.f;
 63         x=e.from;
 64     }
 65     x=t;
 66     while(x!=s)
 67     {
 68         edge[p[x]].f+=a;
 69         edge[p[x]^1].f-=a;
 70         x=edge[p[x]].from ;
 71     }
 72     return a;
 73 }
 74 
 75 int maxflow(int s,int t,int n)
 76 {
 77     int flow=0,i;
 78     bfs(s,t);
 79     memset(num,0,sizeof(num));
 80     memset(cur,0,sizeof(cur));
 81     for(i=0;i<=t;i++)
 82         num[d[i]]++;
 83     int x=s;
 84     while(d[s]<=n)
 85     {
 86         //printf("temp %d\n",flow);
 87         if(x==t)
 88         {
 89             flow+=zg(s,t);
 90             x=s;
 91             //printf("flow  %d\n",flow);
 92         }
 93         int ok=0;
 94         for(i=cur[x];i<g[x].size ();i++)
 95         {
 96             E e;
 97             e=edge[g[x][i]];
 98             if(e.c>e.f&&d[x]==d[e.to]+1)
 99             {
100                 ok=1;
101 
102                 p[e.to]=g[x][i];
103 
104                 cur[x]=i;
105                 x=e.to;//!@#$%^&
106                 break;
107             }
108         }
109         if(ok==0)
110         {
111             int m=n;
112             for(i=0;i<g[x].size ();i++)
113             {
114                 E e;
115                 e=edge[g[x][i]];
116                 if(e.c>e.f&&m>d[e.to])
117                     m=d[e.to];
118             }
119             if(--num[d[x]]==0)  break;
120             num[d[x]=m+1]++;
121             cur[x]=0;////!@#$%^^&
122             if(x!=s)
123                 x=edge[p[x]].from ;
124 
125         }
126     }
127     return flow;
128 }
129 
130 bool ok(int x)
131 {
132     edge.clear();
133     for(int i=0;i<=3*n+1;i++)
134         g[i].clear();
135 
136     for(int i=1;i<=n;i++)
137     {
138         add(0,i,INF);
139         add(i,i+n,you[i]);
140         add(i+2*n,i+3*n,nz[i]);
141         add(i+3*n,4*n+1,INF);
142 
143         for(int j=1;j<=n;j++)
144             if(dis[i][j]<=x)
145                  {
146                      add(i,j+3*n,INF);
147                      add(3*j+n,i,INF);
148                  }
149      }
150     int flow;
151     flow=maxflow(0,4*n+1,4*n+1);
152     //printf("flow %d    x %d\n",flow,x);
153     if(flow==tot)
154         return true;
155     return false;
156 }
157 
158 int solve(int maxe)
159 {
160     int left=0,right=maxe,ans=maxe;
161     while(left<=right)
162     {
163         int mid=(left+right)/2;
164         if(ok(mid))
165         {
166             ans=min(ans,mid);
167             right=mid-1;
168         }
169         else left=mid+1;
170     }
171     return ans;
172 }
173 
174 int main()
175 {
176     int m,a,b,c;
177     while(~scanf("%d%d",&n,&m))
178     {
179         tot=0;
180         for(int i=1;i<=n;i++)
181         {
182             scanf("%d%d",&you[i],&nz[i]);
183             tot+=you[i];
184         }
185         for(int i=1;i<=n;i++)
186             for(int j=1;j<=n;j++)
187                 if(i==j)
188                 dis[i][j]=0;
189             else
190                dis[i][j]=INF;
191         int size1=0;
192         while(m--)
193         {
194             scanf("%d%d%d",&a,&b,&c);
195             dis[a][b]=min(dis[a][b],c);
196             dis[b][a]=min(dis[b][a],c);
197         }
198         int maxe=0;
199         for(int k=1;k<=n;k++)
200             for(int i=1;i<=n;i++)
201                for(int j=1;j<=n;j++)
202                {
203                    dis[i][j]=min(dis[i][k]+dis[k][j],dis[i][j]);
204                    if(k==n)
205                         maxe=max(maxe,dis[i][j]);
206                }
207         printf("%d\n",solve(maxe));
208     }
209     return 0;
210 }