Create 5889_yp_2013.cpp

From http://blog.csdn.net/yp_2013/article/details/52571457

HDOJ/5889_yp_2013.cpp

@@ -0,0 +1,157 @@
+#include<bits/stdc++.h>
+using namespace std;
+const int maxn = 2005;
+#define inf 1e9
+#define INF 1e9
+const int maxm = 4000000+50;
+struct Node
+{
+    int v,w;
+    Node(int vv,int ww):v(vv),w(ww){};
+};
+vector<Node>e[maxn];
+int s,t,n,m,vs,vt;
+int d[maxn];
+int vis[maxn];
+void spfa()
+{
+    memset(vis,0,sizeof(vis));
+    for(int i = 1;i<=n;i++)
+        d[i]=inf;
+    d[s]=0;
+    queue<int>q;
+    q.push(s);
+    while(!q.empty())
+    {
+        int u = q.front();
+        q.pop();
+        vis[u]=0;
+        for(int i = 0;i<e[u].size();i++)
+        {
+            int v = e[u][i].v;
+            int w = e[u][i].w;
+            if(d[v]>d[u]+1)
+            {
+                d[v]=d[u]+1;
+                if(!vis[v])
+                    q.push(v);
+                vis[v]=1;
+            }
+        }
+    }
+}
+
+
+struct Edge
+{
+    int from,to,cap,flow;
+    Edge(int u,int v,int c,int f):from(u),to(v),cap(c),flow(f){}
+};
+struct Dinic
+{
+//  int n,m;
+    int s,t;
+    vector<Edge>edges;        //边数的两倍
+    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
+    bool vis[maxn];           //BFS使用
+    int d[maxn];              //从起点到i的距离
+    int cur[maxn];            //当前弧下标
+    void init()
+    {
+       for (int i=0;i<=n+1;i++)
+           G[i].clear();
+       edges.clear();
+    }
+    void AddEdge(int from,int to,int cap)
+    {
+        edges.push_back(Edge(from,to,cap,0));
+        edges.push_back(Edge(to,from,0,0));        //反向弧
+        int mm=edges.size();
+        G[from].push_back(mm-2);
+        G[to].push_back(mm-1);
+    }
+    bool BFS()
+    {
+        memset(vis,0,sizeof(vis));
+        queue<int>q;
+        q.push(s);
+        d[s]=0;
+        vis[s]=1;
+        while (!q.empty())
+        {
+            int x = q.front();q.pop();
+            for (int i = 0;i<G[x].size();i++)
+            {
+                Edge &e = edges[G[x][i]];
+                if (!vis[e.to] && e.cap > e.flow)
+                {
+                    vis[e.to]=1;
+                    d[e.to] = d[x]+1;
+                    q.push(e.to);
+                }
+            }
+        }
+        return vis[t];
+    }
+
+    int DFS(int x,int a)
+    {
+        if (x==t || a==0)
+            return a;
+        int flow = 0,f;
+        for(int &i=cur[x];i<G[x].size();i++)
+        {
+            Edge &e = edges[G[x][i]];
+            if (d[x]+1 == d[e.to] && (f=DFS(e.to,min(a,e.cap-e.flow)))>0)
+            {
+                e.flow+=f;
+                edges[G[x][i]^1].flow-=f;
+                flow+=f;
+                a-=f;
+                if (a==0)
+                    break;
+            }
+        }
+        return flow;
+    }
+
+    int Maxflow(int s,int t)
+    {
+        this->s=s;
+        this->t=t;
+        int flow = 0;
+        while (BFS())
+        {
+            memset(cur,0,sizeof(cur));
+            flow+=DFS(s,INF);
+        }
+        return flow;
+    }
+}dc;
+
+int main()
+{
+    int T;
+    scanf("%d",&T);
+    while(T--)
+    {
+        scanf("%d%d",&n,&m);
+        for(int i = 0;i<=n;i++)
+            e[i].clear();
+        for(int i = 1;i<=m;i++)
+        {
+            int u,v,di;
+            scanf("%d%d%d",&u,&v,&di);
+            e[u].push_back(Node(v,di));
+            e[v].push_back(Node(u,di));
+        }
+        s=1,t=n;
+        spfa();
+        dc.init();
+        for(int i = 1;i<=n;i++)
+            for(int j = 0;j<e[i].size();j++)
+                if(d[e[i][j].v]==d[i]+1)
+                    dc.AddEdge(i,e[i][j].v,e[i][j].w);
+        printf("%d\n",dc.Maxflow(s,t));
+    }
+}