BZOJ1266/AHOI2006/上学路线

Posted on By 二价氢

我去,500+点裸Floyd居然给过?!BZOJ这评测机不科学的不是一点两点啊!

求完1-i最短路,再求n-i的最短路,两个sssp,上spfa足矣

然后跑个网络流拿dinic练练手……

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
const int maxn=505,maxm=124755,inf=0x7ffffff;
struct edg1{int t,w,v,n;}e1[maxm*2];
struct edg2{int t,v,n;}e2[maxm*2];
int pf1[maxn],pf2[maxn],te1,te2;
int f[maxn][maxn];
int vis[maxn],lay[maxn];
int m,n;
void ae1(int s,int t,int w,int v)
{
    e1[++te1].t=t;
    e1[te1].w=w;
    e1[te1].v=v;
    e1[te1].n=pf1[s];
    pf1[s]=te1;
}
void ae2(int s,int t,int v)
{
    e2[te2].t=t;
    e2[te2].v=v;
    e2[te2].n=pf2[s];
    pf2[s]=te2++;
}
bool build()
{
    memset(vis,0,sizeof(vis));
    memset(lay,-1,sizeof(lay));
    queue<int>Q;
    Q.push(1);lay[1]=0;
    while (!Q.empty())
    {
        int u=Q.front();Q.pop();
        for (int c=pf2[u];~c;c=e2[c].n)
            if (e2[c].v&&lay[e2[c].t]==-1)
            {
                lay[e2[c].t]=lay[u]+1;
                Q.push(e2[c].t);
            }
    }
    return lay[n]!=-1;
}
int find(int u,int low)
{
    if (u==n)
        return low;
    int ans=0;
    for (int c=pf2[u];(~c)&&low;c=e2[c].n)
    {
        int tans;
        if (lay[e2[c].t]==lay[u]+1&&(tans=find(e2[c].t,min(low,e2[c].v))))
        {
            e2[c].v-=tans;
            e2[c^1].v+=tans;
            ans+=tans;
            low-=tans;
        }
    }
    return ans;
}
int dinic()
{
    int ans=0;
    while (build())
    {
        int tans;
        while ((tans=find(1,inf)))
            ans+=tans;
    }
    return ans;
}
int main()
{
    int a,b,c,d;
    scanf("%d%d",&n,&m);
    memset(f,0x3f,sizeof(f));
    memset(pf2,-1,sizeof(pf2));
    for (int i=1;i<=m;i++)
    {
        scanf("%d%d%d%d",&a,&b,&c,&d);
        f[a][b]=f[b][a]=min(f[a][b],c);
        ae1(a,b,c,d);
        ae1(b,a,c,d);
    }
    for (a=1;a<=n;a++)
        f[a][a]=0;
    for (c=1;c<=n;c++)
        for (a=1;a<=n;a++)
            for (b=1;b<=n;b++)
                f[a][b]=min(f[a][b],f[a][c]+f[c][b]);
    for (a=1;a<=n;a++)
        for (b=pf1[a];b;b=e1[b].n)
            if (f[1][a]+e1[b].w+f[e1[b].t][n]==f[1][n])
            {
                ae2(a,e1[b].t,e1[b].v);
                ae2(e1[b].t,a,0);
            }
    printf("%d\n%d\n",f[1][n],dinic());
    return 0;
}