hdu 5889 spfa&最小割

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用spfa处理处最短路，把多条最短路上的边放到新图里面，跑一遍dinic求最小割。
#include<bits/stdc++.h>using namespace std;const int maxn = 2005;#define inf 1e9#define INF 1e9const 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));    }}
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