1 #include <iostream> 2 #include <string.h> 3 #include <stdio.h> 4 #include <algorithm> 5 #include <queue> 6 #define V 10100 7 #define E 1000100 8 #define inf 99999999 9 using namespace std; 10 int vis[V]; 11 int dist[V]; 12 int pre[V]; 13 14 struct Edge{ 15 int u,v,c,cost,next; 16 }edge[E]; 17 int head[V],cnt; 18 19 void init(){ 20 cnt=0; 21 memset(head,-1,sizeof(head)); 22 } 23 void addedge(int u,int v,int c,int cost) 24 { 25 edge[cnt].u=u;edge[cnt].v=v;edge[cnt].cost=cost; 26 edge[cnt].c=c;edge[cnt].next=head[u];head[u]=cnt++; 27 28 edge[cnt].u=v;edge[cnt].v=u;edge[cnt].cost=-cost; 29 edge[cnt].c=0;edge[cnt].next=head[v];head[v]=cnt++; 30 } 31 32 bool spfa(int begin,int end){ 33 int u,v; 34 queue<int> q; 35 for(int i=0;i<=end+2;i++){ 36 pre[i]=-1; 37 vis[i]=0; 38 dist[i]=inf; 39 } 40 vis[begin]=1; 41 dist[begin]=0; 42 q.push(begin); 43 while(!q.empty()){ 44 u=q.front(); 45 q.pop(); 46 vis[u]=0; 47 for(int i=head[u];i!=-1;i=edge[i].next){ 48 if(edge[i].c>0){ 49 v=edge[i].v; 50 if(dist[v]>dist[u]+edge[i].cost){ 51 dist[v]=dist[u]+edge[i].cost; 52 pre[v]=i; 53 if(!vis[v]){ 54 vis[v]=true; 55 q.push(v); 56 } 57 } 58 } 59 } 60 } 61 return dist[end]!=inf; 62 } 63 64 int MCMF(int begin,int end){ 65 int ans=0,flow; 66 int flow_sum=0; 67 while(spfa(begin,end)){ 68 flow=inf; 69 for(int i=pre[end];i!=-1;i=pre[edge[i].u]) 70 if(edge[i].c<flow) 71 flow=edge[i].c; 72 for(int i=pre[end];i!=-1;i=pre[edge[i].u]){ 73 edge[i].c-=flow; 74 edge[i^1].c+=flow; 75 } 76 ans+=dist[end]; 77 flow_sum += flow; 78 } 79 //cout << flow_sum << endl; 80 return ans; 81 } 82 83 int main() 84 { 85 //freopen("in.txt","r",stdin); 86 int n,m,a,b,c; 87 while(scanf("%d%d",&n,&m)!=EOF){ 88 init(); 89 addedge(0,1,2,0); 90 addedge(n,n+1,2,0); 91 for(int i=1;i<=m;i++){ 92 scanf("%d%d%d",&a,&b,&c); 93 addedge(a,b,1,c); 94 addedge(b,a,1,c); 95 } 96 printf("%d ",MCMF(0,n+1)); 97 } 98 return 0; 99 }