C :

#include<stdio.h>
int main()
{
	int n;
	while((scanf("%d",&n))!=EOF)
	{
		int i,j,k,t;
		int a[10][10]={0},s[10][10][10][10]={0};
		int x,y,z;
		for(;;)
		{
			scanf("%d %d %d",&x,&y,&z);
			a[x][y]=z;
			if(x==0&&y==0&&z==0)
				break;
		}
		for(i=1;i<=n;i++)
			for(j=1;j<=n;j++)
				for(k=1;k<=n;k++)
					for(t=1;t<=n;t++)
					{
						if(s[i][j][k][t]<s[i-1][j][k-1][t])
							s[i][j][k][t]=s[i-1][j][k-1][t];
						if(s[i][j][k][t]<s[i-1][j][k][t-1])
							s[i][j][k][t]=s[i-1][j][k][t-1];
						if(s[i][j][k][t]<s[i][j-1][k][t-1])
							s[i][j][k][t]=s[i][j-1][k][t-1];
						if(s[i][j][k][t]<s[i][j-1][k-1][t])
							s[i][j][k][t]=s[i][j-1][k-1][t];
						if(i==k&&j==t)
							s[i][j][k][t]=s[i][j][k][t]+a[i][j];
						else
							s[i][j][k][t]=s[i][j][k][t]+a[i][j]+a[k][t];
					}
		printf("%d\n",s[i-1][j-1][k-1][t-1]);
	}
	return 0;
}

C++ :

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
int a[15][15],f[15][15][15][15];
int max(int a,int b)
{
    return a>b?a:b;
}
int main()
{
    int n,i,j,k,l;
    scanf("%d",&n);
    while(scanf("%d%d%d",&i,&j,&k),i,j,k)
    {
        a[i][j]=k;
    }
    memset(f,0,sizeof(f));
    for(i = 1; i <= n ; i++)
        for( j = 1; j <= n ; j++)
            for( k = 1; k <= n ;k ++)
                for(l = 1 ; l <= n ; l++ )
                {
                    if((i<n||j<n)&&i<=k&&j<=l) continue;
                    int sum = a[1][1] ;
                    sum = max(sum ,f[i-1][j][k-1][l]);
                    sum = max(sum ,f[i][j-1][k][l-1]);
                    if(i-1!=k&&j!=l-1)
                    sum = max(sum ,f[i-1][j][k][l-1]);
                    if(i!=k-1&&j-1!=l)
                    sum = max(sum ,f[i][j-1][k-1][l]);
                    f[i][j][k][l] = sum +a[i][j]+a[k][l];
                }
    printf("%d\n",f[n][n][n][n]-a[n][n]);
    return 0;
}