bzoj 1820 DP

/**************************************************************
    Problem: 1820
    User: BLADEVIL
    Language: C++
    Result: Accepted
    Time:1512 ms
    Memory:2216 kb
****************************************************************/
 
//By BLADEVIL
#include <cstdio>
#include <cstring>
#define maxn 300
#define inf 1<<30
 
using namespace std;
 
int n,ans;
int dis[maxn][maxn],w[3][maxn][maxn],a[1010];
 
void getmin(int &x,int y)
{x=(y>x)?x:y;}
 
int main()
{
    scanf("%d",&n);
    for (int i=1;i<=n;i++)
        for (int j=1;j<=n;j++) scanf("%d",&dis[i][j]);
    memset(w,40,sizeof w);
    w[0][2][3]=w[0][3][2]=0; a[0]=1;
    int q,p;
    p=q=1;
    while (scanf("%d",&a[q])!=EOF)
    {
        memset(w[p],40,sizeof w[p]);
        for (int i=1;i<=n;i++)
            for (int j=1;j<=n;j++)
            {
                getmin(w[p][i][j],w[1-p][i][j]+dis[a[q-1]][a[q]]);
                getmin(w[p][a[q-1]][j],w[1-p][i][j]+dis[i][a[q]]);
                getmin(w[p][a[q-1]][i],w[1-p][i][j]+dis[j][a[q]]);
            }
        p=1-p; q++;
    }
    ans=inf;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=n;j++)
            getmin(ans,w[1-p][i][j]);
    printf("%d\n",ans);
    return 0;
}