题目：http://www.lydsy.com/JudgeOnline/problem.php?id=2151
题解：此题=数据备份。喜闻乐见挂链表。
代码：
1 #include<cstdio> 2 #include<cstdlib> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 #include<iostream> 7 #include<vector> 8 #include<map> 9 #include<set> 10 #include<queue> 11 #include<string> 12 #define inf 1000000000 13 #define maxn 200000+5 14 #define maxm 100000+5 15 #define eps 1e-10 16 #define ll long long 17 #define pa pair<int,int> 18 #define for0(i,n) for(int i=0;i<=(n);i++) 19 #define for1(i,n) for(int i=1;i<=(n);i++) 20 #define for2(i,x,y) for(int i=(x);i<=(y);i++) 21 #define for3(i,x,y) for(int i=(x);i>=(y);i--) 22 #define for4(i,x) for(int i=head[x],y=e[i].go;i;i=e[i].next,y=e[i].go) 23 #define mod 1000000007 24 using namespace std; 25 inline int read() 26 { 27 int x=0,f=1;char ch=getchar(); 28 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 29 while(ch>='0'&&ch<='9'){x=10*x+ch-'0';ch=getchar();} 30 return x*f; 31 } 32 int n,m,a[maxn],l[maxn],r[maxn]; 33 priority_queue<pa>q; 34 int main() 35 { 36 freopen("input.txt","r",stdin); 37 freopen("output.txt","w",stdout); 38 n=read();m=read(); 39 if(m>n>>1){printf("Error! ");return 0;} 40 for1(i,n)a[i]=read(),l[i]=i-1,r[i]=i+1,q.push(pa(a[i],i)); 41 l[1]=n;r[n]=1; 42 int ans=0; 43 for1(i,m) 44 { 45 while(!q.empty()&&q.top().first!=a[q.top().second])q.pop(); 46 int x=q.top().second;q.pop(); 47 ans+=a[x]; 48 a[x]=a[l[x]]+a[r[x]]-a[x];q.push(pa(a[x],x)); 49 a[l[x]]=a[r[x]]=inf; 50 r[l[x]=l[l[x]]]=x;l[r[x]=r[r[x]]]=x; 51 } 52 cout<<ans<<endl; 53 return 0; 54 }