HDU5805 NanoApe Loves Sequence (BestCoder Round #86 B)前后缀预处理

分析：维护空隙的差，然后预处理前缀最大，后缀最大，扫一遍

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 1e5+5;
int a[N],T,n,b[N],l[N],r[N];
int main(){
  scanf("%d",&T);
  while(T--){
   scanf("%d",&n);
   for(int i=1;i<=n;++i)scanf("%d",&a[i]);
   LL ret=0;
   for(int i=1;i<n;++i){
      b[i]=abs(a[i]-a[i+1]);
      l[i]=max(l[i-1],b[i]);
   }
   r[n]=0;
   for(int i=n-1;i>0;--i)r[i]=max(r[i+1],b[i]);
   for(int i=1;i<=n;++i){
     if(i==1)ret+=r[2];
     else if(i==n)ret+=l[n-2];
     else{
       int tmp=max(l[i-2],r[i+1]);
       tmp=max(tmp,abs(a[i+1]-a[i-1]));
       ret+=tmp;
     }
   }
   printf("%I64d
",ret);
  } 
  return 0;
}