dp——环形石子合并（区间dp）
环形的解决很巧妙
1 #include <iostream> 2 #include <cstring> 3 #include <string> 4 #include <map> 5 #include <set> 6 #include <algorithm> 7 #include <fstream> 8 #include <cstdio> 9 #include <cmath> 10 #include <stack> 11 #include <queue> 12 #define lson l,m,rt<<1 13 #define rson m+1,r,rt<<1|1 14 using namespace std; 15 const double Pi=3.14159265358979323846; 16 typedef long long ll; 17 const int MAXN=100+5; 18 const int dx[5]={0,0,0,1,-1}; 19 const int dy[5]={1,-1,0,0,0}; 20 const int INF = 0x3f3f3f3f; 21 const int NINF = 0xc0c0c0c0; 22 const ll mod=1e9+7; 23 24 int a[MAXN*2],dp[MAXN*2][MAXN*2];int sum[MAXN*2];int df[MAXN*2][MAXN*2]; 25 26 int main() 27 { 28 int n;scanf("%d",&n); 29 memset(dp,0,sizeof(dp)); 30 for(int i=1;i<=n;i++) 31 { 32 scanf("%d",&a[i]); 33 sum[i]=sum[i-1]+a[i]; 34 } 35 for(int i=n+1;i<=n+n;i++) 36 { 37 a[i]=a[i-n]; 38 39 sum[i]=sum[i-1]+a[i]; 40 } 41 for(int l=2;l<=n;l++) 42 { 43 44 for(int i=1;i<=n+n;i++) 45 { 46 int j=l+i-1; 47 df[i][j]=INF; 48 if(j>n+n) continue; 49 for(int k=i;k<j;k++) 50 { 51 dp[i][j]=max(dp[i][k]+dp[k+1][j]+sum[j]-sum[i-1],dp[i][j]); 52 df[i][j]=min(df[i][k]+df[k+1][j]+sum[j]-sum[i-1],df[i][j]); 53 } 54 55 } 56 } 57 int ans1=0; 58 int ans2=INF; 59 for(int i=1;i<=n;i++) 60 { 61 int j=i+n-1; 62 if(j>n+n) break; 63 ans1=max(dp[i][j],ans1); 64 ans2=min(df[i][j],ans2); 65 66 } 67 cout << ans2<<endl<<ans1<<endl; 68 return 0; 69 }
