HDU 2845 Beans

/*
*   Author: johnsondu
*   Time : 2013-5-1
*   problems: HDU 2845 Beans
*   url: http://acm.hdu.edu.cn/showproblem.php?pid=2845
*   stratege: dynamic programming
*   state transition equation:  dp[i] = max (dp[i-1], dp[i-2] + dp[i]) ; Attention to boarder
*/
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std ;

#define N 200005
#define min(x, y) (x < y ? x : y)
#define max(x, y) (x > y ? x : y)
int dp[N] ;
int sum[N] ;
int n, m, ans ;

int main()
{
    //freopen ("data.txt", "r", stdin) ;
    while (scanf ("%d%d", &n, &m) != EOF)
    {
        memset (sum, 0, sizeof (sum)) ;
        memset (dp, 0, sizeof (dp)) ;
        for (int i = 1; i <= n; i ++)       //count on every row's max value, and store it to sum
        {
            for (int j = 1; j <= m; j ++)
                scanf ("%d", &dp[j]) ;
            for (int j = 2; j <= m; j ++)
                dp[j] = max (dp[j-1], dp[j-2] + dp[j]) ;
            sum[i] = dp[m] ;
        }
        for (int i = 2; i <= n; i ++)           //count the max value.
            sum[i] = max (sum[i-1], sum[i-2] + sum[i]) ;
        printf ("%d\n", sum[n]) ;
    }
    return 0 ;
}