【cogs 775】山海经 ——Segment Tree

 1 #define Troy 
 2 
 3 #include <bits/stdc++.h>
 4 
 5 using namespace std;
 6 
 7 inline int read(){
 8     int s=0,k=1;char ch=getchar();
 9     while(ch<‘0‘|ch>‘9‘)    ch==‘-‘?k=-1:0,ch=getchar();
10     while(ch>47&ch<=‘9‘)    s=s*10+(ch^48),ch=getchar();
11     return s*k;
12 }
13 
14 const int N=100005;
15 
16 int n,m,a[N];
17 
18 struct node {
19     int l,r,val;
20     friend bool operator <(node x,node y){
21         return x.val!=y.val?x.val<y.val:(x.l!=y.l?x.l>y.l:x.r>y.r);
22     }
23     friend node operator +(node x,node y){
24         node z;
25         z.l=min(x.l,y.l);z.r=max(x.r,y.r);
26         z.val=x.val+y.val;return z;
27     }
28     inline void out(){printf("%d %d %d\n",l,r,val);}
29 };
30 
31 struct Tree{
32     node prefix,suffix,middle,section;
33     Tree *lc,*rc;
34 }*root,tree[N*20],*ans;int cnt;
35 
36 inline void update( Tree *u){
37     u->middle=u->lc->suffix+u->rc->prefix;
38     u->prefix=max(u->lc->prefix,u->lc->section+u->rc->prefix);
39     u->suffix=max(u->rc->suffix,u->rc->section+u->lc->suffix);
40     u->section=u->lc->section+u->rc->section;
41     u->middle=max(u->middle,max(u->lc->middle,max(u->rc->middle,max(u->prefix,u->suffix))));
42 }
43 
44 inline void build(Tree *&u,int l,int r){
45     u=tree+cnt;++cnt;
46     if(l==r){
47         u->prefix=u->suffix=u->middle=u->section=(node){l,r,a[l]};
48         return ;
49     }
50     int mid=l+r>>1;
51     build(u->lc,l,mid);
52     build(u->rc,mid+1,r);
53     update(u);
54 }
55 
56 inline void query(Tree *u,int l,int r,int x,int y){
57     if(x<=l&&r<=y){
58         if(ans==NULL)   ans=u;
59         else{
60             Tree *now=ans;ans=tree+cnt,++cnt;
61             ans->lc=now,ans->rc=u;
62             update(ans);
63         }
64         return ;
65     }
66     int mid=l+r>>1;
67     if(x<=mid)  query(u->lc,l,mid,x,y);
68     if(y>mid)   query(u->rc,mid+1,r,x,y);  
69 }
70 
71 int main(){
72     freopen("hill.in","r",stdin);
73     freopen("hill.out","w",stdout);
74     n=read(),m=read();
75     for(int i=1;i<=n;++i)   a[i]=read();
76     build(root,1,n);
77     for(int i=1;i<=m;++i){
78         int l=read(),r=read();
79         ans=NULL;query(root,1,n,l,r);
80         ans->middle.out();
81     }
82 }