wikioi 1043 双向dfs

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<map>
#include<queue>
#include<set>
#include<cmath>
#include<bitset>
#define mem(a,b) memset(a,b,sizeof(a))
#define lson i<<1,l,mid
#define rson i<<1|1,mid+1,r
#define llson j<<1,l,mid
#define rrson j<<1|1,mid+1,r
#define INF 0x7fffffff
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
int n,a[10][11],Max;
void dfs2(int i,int j,int sum)
{
    if(i==1&&j==1) Max=max(Max,sum);
    else
    {
        if(i>1&&a[i-1][j]!=-1) dfs2(i-1,j,sum+a[i][j]);
        if(j>1&&a[i][j-1]!=-1) dfs2(i,j-1,sum+a[i][j]);
    }
}
void dfs1(int i,int j,int sum)
{
    if(i==n&&j==n) a[1][1]=0,dfs2(n,n,sum);
    else
    {
        int cnt=a[i][j];a[i][j]=-1;
        if(i<n) dfs1(i+1,j,sum+cnt);
        if(j<n) dfs1(i,j+1,sum+cnt);
        a[i][j]=cnt;
    }
}
int main()
{
    int u,v,w;
    scanf("%d",&n);
    while(~scanf("%d%d%d",&u,&v,&w))
    {
        if(u==0&&v==0&&w==0) break;
        a[u][v]=w;
    }
    dfs1(1,1,0);
    cout<<Max<<endl;
    return 0;
}