学步园

先对从左到右对每一行进行dp，再类似地从上到下dp，两次dp！

#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <deque>
#include <stack>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <limits.h>
#include <time.h>
#include <string.h>
using namespace std;

int lowbit(int t){return t&(-t);}
int countbit(int t){return (t==0)?0:(1+countbit(t&(t-1)));}
int gcd(int a,int b){return (b==0)?a:gcd(b,a%b);}
#define LL long long
#define PI acos(-1.0)
#define N  200001
#define Max INT_MAX
#define Min INT_MIN
#define eps 1e-8
#define FRE freopen("a.txt","r",stdin)
int dp1[N],b[N],dp2[N];
int main(){
    int n,m;
    while(scanf("%d%d",&n,&m)!=EOF){
        int i,j,k;
        for(i=1;i<=n;i++){
            for(j=1;j<=m;j++){
                int a;
                scanf("%d",&a);
                dp1[0]=0;
                if(j==1)dp1[j]=a;
                else{
                    dp1[j]=max(dp1[j-1], dp1[j-2]+a);
                }
            }
            b[i]=dp1[m];
        }
        dp2[1]=b[1];
        dp2[0]=0;
        for(i=2;i<=n;i++)
        dp2[i]=max(dp2[i-1],dp2[i-2]+b[i]);
        printf("%d\n",dp2[n]);
    }
    return 0;
}