COJ 0252 HDNOIP201304阻断传染

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<algorithm>
 5 #include<queue>
 6 #include<cstring>
 7 #define PAU putchar(‘ ‘)
 8 #define ENT putchar(‘\n‘)
 9 using namespace std;
10 const int maxn=100000+10,maxm=200000+10,inf=-1u>>1;
11 int out[maxn];
12 struct isap{
13     struct ted{int x,y,w;ted*nxt,*re;}adj[maxm],*fch[maxn],*ms,*cur[maxn],*ret[maxn];
14     int d[maxn],gap[maxn],n,S,T;
15     void init(int n){this->n=n;memset(d,-1,sizeof(d));ms=adj;return;}
16     void add(int x,int y,int w){
17         *ms=(ted){x,y,w,fch[x],ms+1};fch[x]=ms++;
18         *ms=(ted){y,x,0,fch[y],ms-1};fch[y]=ms++;
19         return;
20     }
21     void bfs(){
22         queue<int>Q;Q.push(T);d[T]=0;
23         while(!Q.empty()){
24             int u=Q.front();Q.pop();
25             for(ted*e=fch[u];e;e=e->nxt){
26                 int v=e->y;if(d[v]<0)d[v]=d[u]+1,Q.push(v);
27             }
28         } return;
29     }
30     int mxflow(int S,int T){
31         this->S=S;this->T=T;bfs();ted*e;int k=S,flow=0;
32         for(int i=1;i<=n;i++)gap[d[i]]++,cur[i]=fch[i];
33         while(d[S]<n){
34             if(k==T){
35                 int mi=inf,pos;for(int i=S;i!=T;i=cur[i]->y)if(cur[i]->w<mi)mi=cur[i]->w,pos=i;
36                 for(int i=S;i!=T;i=cur[i]->y)cur[i]->w-=mi,cur[i]->re->w+=mi;flow+=mi;k=pos;
37             } for(e=cur[k];e;e=e->nxt)if(e->w&&d[k]==d[e->y]+1)break;
38             if(e)cur[k]=e,ret[e->y]=e->re,k=e->y;
39             else{if(--gap[d[k]]==0)break;cur[k]=fch[k];int mi=n;
40                 for(e=fch[k];e;e=e->nxt)if(e->w&&d[e->y]<mi)mi=d[e->y];
41                 d[k]=mi+1;gap[d[k]]++;if(k!=S)k=ret[k]->y;
42             }
43         } return flow;
44     }
45 }sol;
46 struct ted{int x,y,w;ted*nxt;}adj[maxm],*fch[maxn],*ms=adj;
47 void add(int x,int y,int w){
48     *ms=(ted){x,y,w,fch[x]};fch[x]=ms++;
49     *ms=(ted){y,x,w,fch[y]};fch[y]=ms++;
50     return;
51 }
52 bool vis[maxn];
53 void bfs(int S){
54     queue<int>Q;Q.push(S);vis[S]=true;
55     while(!Q.empty()){
56         int u=Q.front();Q.pop();
57         for(ted*e=fch[u];e;e=e->nxt){
58             int v=e->y;if(!vis[v]){
59                 vis[v]=true;out[u]++;sol.add(u,v,e->w);Q.push(v);//printf("add:%d->%d %d\n",u,v,e->w);system("pause");
60             }
61         }
62     } return;
63 }
64 int n,m;queue<int>tset;
65 void makeG(){
66     for(int i=1;i<=n;i++)if(!out[i])tset.push(i);//printf("tset:");
67     while(!tset.empty()){
68         int x=tset.front();tset.pop();sol.add(x,n+1,1e9);//printf("%d ",x);
69     } return;
70 }
71 inline int read(){
72     int x=0,sig=1;char ch=getchar();
73     while(!isdigit(ch)){if(ch==‘-‘) sig=-1;ch=getchar();}
74     while(isdigit(ch)) x=10*x+ch-‘0‘,ch=getchar();
75     return x*=sig;
76 }
77 inline void write(int x){
78     if(x==0){putchar(‘0‘);return;}if(x<0) putchar(‘-‘),x=-x;
79     int len=0,buf[15];while(x) buf[len++]=x%10,x/=10;
80     for(int i=len-1;i>=0;i--) putchar(buf[i]+‘0‘);return;
81 }
82 void init(){
83     n=read();m=~-n;sol.init(n+1);int x,y,w;
84     for(int i=1;i<=m;i++){
85         x=read();y=read();w=read();add(x,y,w);
86     }bfs(1);makeG();write(sol.mxflow(1,n+1));
87     return;
88 }
89 void work(){
90     return;
91 }
92 void print(){
93     return;
94 }
95 int main(){
96     init();work();print();return 0;
97 }