NOIP2006 Energy Necklace

energy necklace

 

https://www.luogu.org/problemnew/show/P1063

 

Seems more watery than merging pebbles. .

Interval moving gauge, f[l][r] represents the maximum energy of the combined interval l~r

By interval length dp

enumerate intermediate points k

f[l][r]=max(f[l][r],f[l][k]+f[k+1][r]+s[l][0]*s[r][1]*s[k][1]);

For loops, make a chain of twice the length

 

 

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 #define ll long long
 5 using namespace std;
 6 const int MAXN = 210 ;
 7 ll n,s[MAXN][2],f[MAXN][MAXN];
 8 int main()
 9 {
10     scanf("%lld",&n);
11     for(int i=1;i<=n;i++)
12     {
13         scanf("%lld",&s[i][0]);
14         s[i-1+n][1]=s[i-1][1]=s[i+n][0]=s[i][0];
15     }
16     s[n<<1][1]=s[1][0];
17     for(int len=2;len<=n;len++)
18      for(int l=1;l+len-1<=(n<<1);l++)
19      {
20          int r=l+len-1;
21          for(int k=l;k<r;k++)
22           f[l][r]=max(f[l][r],f[l][k]+f[k+1][r]+s[l][0]*s[r][1]*s[k][1]);
23      }
24     ll ans=0;
25     for(int i=1;i<=n;i++)
26      ans=max(ans,f[i][i+n-1]);
27     printf("%lld\n",years);
28      return  0 ;
29 }