hdu 1024 Max Sum Plus Plus

http://acm.hdu.edu.cn/showproblem.php?pid=1024

状态转移方程： dp[j]=max(dp[j-1]+a[j],pre[j-1]+a[j]);

#include <cstdio>
#include <cstring>
#include <algorithm>
#define maxn 1000010
#define ll int
using namespace std;
const int inf=1<<29;

ll dp[maxn],pre[maxn];
int a[maxn];
int n,m;
ll max2;

ll max1(ll a,ll b)
{
    if(a>b) return a;
    return b;
}

int main()
{
    while(scanf("%d%d",&m,&n)!=EOF)
    {
        for(int i=1; i<=n; i++)
        {
            scanf("%d",&a[i]);
        }
        memset(dp,0,sizeof(dp));
        memset(pre,0,sizeof(pre));
        for(int i=1; i<=m; i++)
        {
            max2=-inf;
            for(int j=i; j<=n; j++)
            {
                dp[j]=max(dp[j-1]+a[j],pre[j-1]+a[j]);
                pre[j-1]=max2;
                max2=max(max2,dp[j]);
            }
        }
        printf("%d
",max2);
    }
    return 0;
}