POJ 3469 dual core cpu ---ISAP

/*这个题目的构图还是不错的，关键是最大流最小割定理的理解程度，算法用的是ISAP，效率还不错。 需要注意的是比如这句话 edge[index].pair = ++index,不同的编译器对这句话的翻译是不一样的， 主要是对++index的处理，有的是先对++index处理：++index，edge[index].pair = index，而有的不是, 可能翻译成:edge[index].pair = index + 1;++index,就是在这个地方WA了好几次，这种错误真是太难检查 了、、、、归根结蒂还是自己对语言了解部透彻，编码习惯不太好。。。。*/

 

#include  < iostream >
#include  < cstdio >
#include  < memory.h >
using   namespace  std;

#define  MAXN 30020
#define  MAXE 2000000
#define  INF 0x3fffffff

int  ne,nv,index,s,t,net[MAXN];
struct  Edge{
     int  next,pair;
     int  v,cap,flow;
}edge[MAXE];
void  add( const   int &  u, const   int &  v, const   int &  val)
{
    edge[index].next  =  net[u];
    net[u]  =  index;
    edge[index].v  =  v;
    edge[index].cap  =  val;
    edge[index].flow  =   0 ;
    edge[index].pair  =  index + 1 ;
     ++ index;
    edge[index].next  =  net[v];
    net[v]  =  index; 
    edge[index].v  =  u;
    edge[index].cap  =   0 ;
    edge[index].flow  =   0 ;
    edge[index].pair  =  index  -   1 ;
     ++ index;
}
int  ISAP()
{
     long  numb[MAXN],dist[MAXN],curedge[MAXN],pre[MAXN];
     long  cur_flow,max_flow,u,tmp,neck,i;
    memset(dist, 0 , sizeof (dist));
    memset(numb, 0 , sizeof (numb));
     for (i  =   1  ; i  <=  nv ;  ++ i)
        curedge[i]  =  net[i];
    numb[nv]  =  nv;
    max_flow  =   0 ;
    u  =  s;
     while (dist[s]  <  nv)
    {
         /*  first , check if has augmemt flow  */
         if (u  ==  t)
        {
            cur_flow  =  INF;
             for (i  =  s; i  !=  t;i  =  edge[curedge[i]].v) 
            {  
                 if (cur_flow  >  edge[curedge[i]].cap)
                {
                    neck  =  i;
                    cur_flow  =  edge[curedge[i]].cap;
                }
            }
             for (i  =  s; i  !=  t; i  =  edge[curedge[i]].v)
            {
                tmp  =  curedge[i];
                edge[tmp].cap  -=  cur_flow;
                edge[tmp].flow  +=  cur_flow;
                tmp  =  edge[tmp].pair;
                edge[tmp].cap  +=  cur_flow;
                edge[tmp].flow  -=  cur_flow;
            }

            max_flow  +=  cur_flow;
            u  =  s;
        }
         /*  if .... else ...  */
         for (i  =  curedge[u]; i  !=   - 1 ; i  =  edge[i].next)
             if (edge[i].cap  >   0   &&  dist[u]  ==  dist[edge[i].v] + 1 )
                 break ;
         if (i  !=   - 1 )
        {
            curedge[u]  =  i;
            pre[edge[i].v]  =  u;
            u  =  edge[i].v;
        } else {
             if ( 0   ==   -- numb[dist[u]])  break ;
            curedge[u]  =  net[u];
             for (tmp  =  nv,i  =  net[u]; i  !=   - 1 ; i  =  edge[i].next)
                 if (edge[i].cap  >   0 )
                    tmp  =  tmp < dist[edge[i].v] ? tmp:dist[edge[i].v];
            dist[u]  =  tmp  +   1 ;
             ++ numb[dist[u]];
             if (u  !=  s) u  =  pre[u];
        }
    }
     return  max_flow;
}
int  main()
{
     int  n,m,i,j,val,a,b;
    index  =   0 ;
    scanf( " %d%d " , & n, & m);
    s  =  n  +   1 ;
    t  =  n  +   2 ;
    nv  =  t;
    memset(net, - 1 , sizeof (net));
     for (i  =   1 ;i  <=  n;  ++ i)
    {
        scanf( " %d%d " , & a, & b);
        add(s,i,a);
        add(i,t,b);
    }
     for (i  =   1 ;i  <=  m;  ++ i)
    {
        scanf( " %d%d%d " , & a, & b, & val);
        edge[index].next  =  net[a];
        net[a]  =  index;
        edge[index].v  =  b;
        edge[index].cap  =  val;
        edge[index].flow  =   0 ;
        edge[index].pair  =  index + 1 ;
         ++ index;
        edge[index].next  =  net[b];
        net[b]  =  index;
        edge[index].v  =  a;
        edge[index].cap  =  val;
        edge[index].flow  =   0 ;
        edge[index].pair  =  index  -   1 ;
         ++ index;
    }
    printf( " %d\n " ,ISAP());
     return   0 ;
}