BZOJ2151: 种树

 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!\n");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 }