OJ-Problems-Source/HDOJ/3599_autoAC.cpp

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#include<iostream>
#include<cstdio>
#include<string.h>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
#define MAXN 4444
#define inf 1<<30
struct Node{
int v,w;
Node(int vv,int ww):v(vv),w(ww){};
};
int n;
bool mark[MAXN];
int dist[MAXN];
vector<vector<Node> >G;
void spfa()
{
memset(mark,false,sizeof(mark));
fill(dist,dist+n+2,inf);
dist[1]=0;
queue<int>que;
que.push(1);
while(!que.empty()){
int u=que.front();
que.pop();
mark[u]=false;
for(int i=0;i<G[u].size();i++){
int v=G[u][i].v;
int w=G[u][i].w;
if(dist[u]+w<dist[v]){
dist[v]=dist[u]+w;
if(!mark[v]){
mark[v]=true;
que.push(v);
}
}
}
}
}
struct Edge{
int v,cap,next;
}edge[MAXN*MAXN];
int NE,NV;
int head[MAXN];
void Insert(int u,int v,int cap)
{
edge[NE].v=v;
edge[NE].cap=cap;
edge[NE].next=head[u];
head[u]=NE++;
edge[NE].v=u;
edge[NE].cap=0;
edge[NE].next=head[v];
head[v]=NE++;
}
void Build()
{
NE=0;
NV=n;
memset(head,-1,sizeof(head));
for(int u=1;u<=n;u++){
for(int i=0;i<G[u].size();i++){
int v=G[u][i].v,w=G[u][i].w;
if(dist[u]+w==dist[v]){
Insert(u,v,1);
}
}
}
}
int level[MAXN],gap[MAXN];
void bfs(int vt)
{
memset(level,-1,sizeof(level));
memset(gap,0,sizeof(gap));
queue<int>que;
que.push(vt);
level[vt]=0;
gap[level[vt]]++;
while(!que.empty()){
int u=que.front();
que.pop();
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(level[v]!=-1)continue;
level[v]=level[u]+1;
gap[level[v]]++;
que.push(v);
}
}
}
int pre[MAXN],cur[MAXN];
int SAP(int vs,int vt)
{
bfs(vt);
memset(pre,-1,sizeof(pre));
memcpy(cur,head,sizeof(head));
int u=pre[vs]=vs,aug=inf,maxflow=0;
gap[0]=NV;
while(level[vs]<NV){
bool flag=false;
for(int &i=cur[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(edge[i].cap>0&&level[u]==level[v]+1){
flag=true;
aug=min(aug,edge[i].cap);
pre[v]=u;
u=v;
if(v==vt){
maxflow+=aug;
for(u=pre[v];v!=vs;v=u,u=pre[u]){
edge[cur[u]].cap-=aug;
edge[cur[u]^1].cap+=aug;
}
aug=inf;
}
break;
}
}
if(flag)continue;
int minlevel=NV;
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(edge[i].cap>0&&level[v]<minlevel){
minlevel=level[v];
cur[u]=i;
}
}
if(--gap[level[u]]==0)break;
level[u]=minlevel+1;
gap[level[u]]++;
u=pre[u];
}
return maxflow;
}
int main()
{
int _case,u,v,w;
scanf("%d",&_case);
while(_case--){
scanf("%d",&n);
G.clear();
G.resize(n+2);
while(true){
scanf("%d%d%d",&u,&v,&w);
if(u==0&&v==0&&w==0)break;
G[u].push_back(Node(v,w));
G[v].push_back(Node(u,w));
}
spfa();
if(dist[n]==inf||n==1){
puts("0");
continue;
}
Build();
printf("%d\n",SAP(1,n));
}
return 0;
}