cf 762D. Maximum path

 1 #include<bits/stdc++.h> 
 2 #define LL long long 
 3 #define N 100005
 4 #define lowbit(x) x&(-x)
 5 using namespace std;
 6 inline int ra()
 7 {
 8     int x=0,f=1; char ch=getchar();
 9     while (ch<‘0‘ || ch>‘9‘) {if (ch==‘-‘) f=-1; ch=getchar();}
10     while (ch>=‘0‘ && ch<=‘9‘) {x=x*10+ch-‘0‘; ch=getchar();}
11     return x*f;
12 }
13 const LL INF=1e16;
14 LL f[N][4];
15 int a[3][N];
16 inline LL sum(int x, int l, int r)
17 {
18     if (l>r) swap(l,r);
19     LL ret=0;
20     for (int i=l; i<=r; i++) ret+=a[i][x];
21     return ret; 
22 }
23 int main()
24 {
25     int n=ra();
26     for (int i=0; i<3; i++)
27         for (int j=1; j<=n; j++)
28             a[i][j]=ra();
29     for (int i=0; i<=n; i++)
30         for (int j=0; j<4; j++)    
31             f[i][j]=-INF;
32     f[0][0]=0;
33     for (int i=1; i<=n; i++)
34     {
35         for (int j=0; j<3; j++)
36             for (int k=0; k<3; k++)
37                 f[i][j]=max(f[i][j],f[i-1][k]+sum(i,j,k));
38         f[i][0]=max(f[i][0],f[i-1][3]+sum(i,0,2));
39         f[i][2]=max(f[i][2],f[i-1][3]+sum(i,0,2));
40         f[i][3]=max(f[i][3],max(f[i-1][0],f[i-1][2])+sum(i,0,2));    
41     }
42     cout<<f[n][2];
43     return 0;
44 }