最大流(Dinic模板)
http://acm.hdu.edu.cn/showproblem.php?pid=1532
1 #include<cstdio> 2 #include<cstring> 3 #include<queue> 4 #include<cmath> 5 using namespace std; 6 const int Ni = 210; 7 const int MAX = 1<<26; 8 struct Edge{ 9 int u,v,c; 10 int next; 11 }edge[20*Ni]; 12 int n,m; 13 int edn;//边数 14 int p[Ni];//父亲 15 int d[Ni]; 16 int sp,tp;//原点，汇点 17 18 void addedge(int u,int v,int c) 19 { 20 edge[edn].u=u; edge[edn].v=v; edge[edn].c=c; 21 edge[edn].next=p[u]; p[u]=edn++; 22 23 edge[edn].u=v; edge[edn].v=u; edge[edn].c=0; 24 edge[edn].next=p[v]; p[v]=edn++; 25 } 26 int bfs() 27 { 28 queue <int> q; 29 memset(d,-1,sizeof(d)); 30 d[sp]=0; 31 q.push(sp); 32 while(!q.empty()) 33 { 34 int cur=q.front(); 35 q.pop(); 36 for(int i=p[cur];i!=-1;i=edge[i].next) 37 { 38 int u=edge[i].v; 39 if(d[u]==-1 && edge[i].c>0) 40 { 41 d[u]=d[cur]+1; 42 q.push(u); 43 } 44 } 45 } 46 return d[tp] != -1; 47 } 48 int dfs(int a,int b) 49 { 50 int r=0; 51 if(a==tp)return b; 52 for(int i=p[a];i!=-1 && r<b;i=edge[i].next) 53 { 54 int u=edge[i].v; 55 if(edge[i].c>0 && d[u]==d[a]+1) 56 { 57 int x=min(edge[i].c,b-r); 58 x=dfs(u,x); 59 r+=x; 60 edge[i].c-=x; 61 edge[i^1].c+=x; 62 } 63 } 64 if(!r)d[a]=-2; 65 return r; 66 } 67 68 int dinic(int sp,int tp) 69 { 70 int total=0,t; 71 while(bfs()) 72 { 73 while(t=dfs(sp,MAX)) 74 total+=t; 75 } 76 return total; 77 } 78 int main() 79 { 80 int i,u,v,c; 81 while(~scanf("%d%d",&m,&n)) 82 { 83 edn=0;//初始化 84 memset(p,-1,sizeof(p)); 85 sp=1;tp=n; 86 for(i=0;i<m;i++) 87 { 88 scanf("%d%d%d",&u,&v,&c); 89 addedge(u,v,c); 90 } 91 printf("%d\n",dinic(sp,tp)); 92 } 93 return 0; 94 }
