hdu 1024 Max Sum Plus Plus(m段最大和)

#include <cstdio>
#include <map>
#include <iostream>
#include<cstring>
#include<bits/stdc++.h>
#define ll long long int
#define M 6
using namespace std;
inline ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
inline ll lcm(ll a,ll b){return a/gcd(a,b)*b;}
int moth[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int dir[4][2]={1,0 ,0,1 ,-1,0 ,0,-1};
int dirs[8][2]={1,0 ,0,1 ,-1,0 ,0,-1, -1,-1 ,-1,1 ,1,-1 ,1,1};
const int inf=0x3f3f3f3f;
const ll mod=1e9+7;
int m,n;
int a[1000007];
int dp1[1000007];
int dp2[1000007];
int main(){
    //ios::sync_with_stdio(false);
    while(~scanf("%d%d",&m,&n)){
        memset(dp1,0,sizeof(dp1));
        memset(dp2,0,sizeof(dp2));
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
        int maxn;
        for(int i=1;i<=m;i++){ //枚举子序列
            maxn=-inf;
            for(int j=i;j<=n;j++){ //j = i是因为每个子序列最少1个元素
                dp1[j]=max(dp2[j-1]+a[j],dp1[j-1]+a[j]);
                dp2[j-1]=maxn;
                maxn=max(maxn,dp1[j]);
            }    
        }
        cout<<maxn<<endl;    
    }
}