<span>UVALive 5790 Ball Stacking（灵活转换）</span>

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <algorithm>
using namespace std;
int a[1005][1005],sum[1005][1005],dp[1005][1005];
int main()
{
    //freopen("in.txt","r",stdin);
    int n;
    while(~scanf("%d",&n)&&n)
    {
        memset(dp,0,sizeof(dp));
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=i; j++)
            {
                scanf("%d",&a[i-j+1][j]);
            }
        }
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=n-i+1; j++)
            {
                sum[i][j]=sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1]+a[i][j];
            }
        }
        int ans=0;
        for(int i=1; i<=n; i++)
        {
            int best=n-i+2;
            for(int j=n-i+1; j>0; j--)
            {
                if(dp[i-1][best]<dp[i-1][j]) best=j;
                dp[i][j]=dp[i-1][best]+sum[i][j]-sum[i-1][j];
                if(dp[i][j]>ans) ans=dp[i][j];
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}