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