158 lines
3.4 KiB
C++
158 lines
3.4 KiB
C++
#include<bits/stdc++.h>
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using namespace std;
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const int maxn = 2005;
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#define inf 1e9
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#define INF 1e9
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const int maxm = 4000000+50;
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struct Node
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{
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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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vector<Node>e[maxn];
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int s,t,n,m,vs,vt;
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int d[maxn];
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int vis[maxn];
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void spfa()
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{
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memset(vis,0,sizeof(vis));
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for(int i = 1;i<=n;i++)
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d[i]=inf;
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d[s]=0;
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queue<int>q;
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q.push(s);
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while(!q.empty())
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{
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int u = q.front();
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q.pop();
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vis[u]=0;
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for(int i = 0;i<e[u].size();i++)
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{
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int v = e[u][i].v;
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int w = e[u][i].w;
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if(d[v]>d[u]+1)
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{
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d[v]=d[u]+1;
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if(!vis[v])
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q.push(v);
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vis[v]=1;
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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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{
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int from,to,cap,flow;
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Edge(int u,int v,int c,int f):from(u),to(v),cap(c),flow(f){}
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};
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struct Dinic
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{
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// int n,m;
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int s,t;
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vector<Edge>edges; //边数的两倍
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vector<int> G[maxn]; //邻接表，G[i][j]表示结点i的第j条边在e数组中的序号
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bool vis[maxn]; //BFS使用
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int d[maxn]; //从起点到i的距离
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int cur[maxn]; //当前弧下标
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void init()
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{
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for (int i=0;i<=n+1;i++)
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G[i].clear();
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edges.clear();
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}
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void AddEdge(int from,int to,int cap)
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{
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edges.push_back(Edge(from,to,cap,0));
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edges.push_back(Edge(to,from,0,0)); //反向弧
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int mm=edges.size();
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G[from].push_back(mm-2);
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G[to].push_back(mm-1);
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}
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bool BFS()
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{
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memset(vis,0,sizeof(vis));
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queue<int>q;
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q.push(s);
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d[s]=0;
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vis[s]=1;
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while (!q.empty())
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{
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int x = q.front();q.pop();
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for (int i = 0;i<G[x].size();i++)
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{
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Edge &e = edges[G[x][i]];
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if (!vis[e.to] && e.cap > e.flow)
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{
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vis[e.to]=1;
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d[e.to] = d[x]+1;
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q.push(e.to);
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}
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}
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}
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return vis[t];
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}
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int DFS(int x,int a)
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{
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if (x==t || a==0)
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return a;
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int flow = 0,f;
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for(int &i=cur[x];i<G[x].size();i++)
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{
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Edge &e = edges[G[x][i]];
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if (d[x]+1 == d[e.to] && (f=DFS(e.to,min(a,e.cap-e.flow)))>0)
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{
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e.flow+=f;
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edges[G[x][i]^1].flow-=f;
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flow+=f;
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a-=f;
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if (a==0)
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break;
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}
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}
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return flow;
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}
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int Maxflow(int s,int t)
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{
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this->s=s;
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this->t=t;
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int flow = 0;
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while (BFS())
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{
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memset(cur,0,sizeof(cur));
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flow+=DFS(s,INF);
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}
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return flow;
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}
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}dc;
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int main()
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{
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int T;
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scanf("%d",&T);
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while(T--)
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{
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scanf("%d%d",&n,&m);
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for(int i = 0;i<=n;i++)
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e[i].clear();
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for(int i = 1;i<=m;i++)
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{
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int u,v,di;
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scanf("%d%d%d",&u,&v,&di);
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e[u].push_back(Node(v,di));
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e[v].push_back(Node(u,di));
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}
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s=1,t=n;
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spfa();
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dc.init();
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for(int i = 1;i<=n;i++)
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for(int j = 0;j<e[i].size();j++)
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if(d[e[i][j].v]==d[i]+1)
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dc.AddEdge(i,e[i][j].v,e[i][j].w);
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printf("%d\n",dc.Maxflow(s,t));
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}
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}
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