SP1043 GSS1 – Can you answer these queries I（猫树）[亲测有效]

 1 //minamoto
 2 #include<iostream>
 3 #include<cstdio>
 4 using namespace std;
 5 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
 6 char buf[1<<21],*p1=buf,*p2=buf;
 7 int read(){
 8     #define num ch-'0'
 9     char ch;bool flag=0;int res;
10     while(!isdigit(ch=getc()))
11     (ch=='-')&&(flag=true);
12     for(res=num;isdigit(ch=getc());res=res*10+num);
13     (flag)&&(res=-res);
14     #undef num
15     return res;
16 }
17 char sr[1<<21],z[20];int C=-1,Z;
18 inline void Ot(){fwrite(sr,1,C+1,stdout),C=-1;}
19 void print(int x){
20     if(C>1<<20)Ot();if(x<0)sr[++C]=45,x=-x;
21     while(z[++Z]=x%10+48,x/=10);
22     while(sr[++C]=z[Z],--Z);sr[++C]='\n';
23 }
24 const int N=5e+5;
25 int n,m,a[N],len,log[N],pos[N],p[21][N],s[21][N];
26 void build(int pp,int l,int r,int d){
27     if(l==r) return (void)(pos[l]=pp);
28     int mid=(l+r)>>1,prep,sm;
29     p[d][mid]=s[d][mid]=sm=prep=a[mid];
30     if(sm<0) sm=0;
31     for(int i=mid-1;i>=l;--i){
32         prep+=a[i],sm+=a[i];
33         s[d][i]=max(s[d][i+1],prep),
34         p[d][i]=max(p[d][i+1],sm);
35         if(sm<0) sm=0;
36     }
37     p[d][mid+1]=s[d][mid+1]=sm=prep=a[mid+1];
38     if(sm<0) sm=0;
39     for(int i=mid+2;i<=r;++i){
40         prep+=a[i],sm+=a[i];
41         s[d][i]=max(s[d][i-1],prep),
42         p[d][i]=max(p[d][i-1],sm);
43         if(sm<0) sm=0;
44     }
45     build(pp<<1,l,mid,d+1);
46     build(pp<<1|1,mid+1,r,d+1);
47 }
48 int query(int l,int r){
49     if(l==r) return a[l];
50     int d=log[pos[l]]-log[pos[l]^pos[r]];
51     return max(max(p[d][l],p[d][r]),s[d][l]+s[d][r]);
52 }
53 int main(){
54 //    freopen("testdata.in","r",stdin);
55     n=read();for(int i=1;i<=n;++i) a[i]=read();
56     len=2;while(len<n) len<<=1;
57     for(int i=2,l=len<<1;i<=l;++i) log[i]=log[i>>1]+1;
58     build(1,1,len,1);
59     m=read();
60     while(m--){
61         int l=read(),r=read();
62         print(query(l,r));
63     }
64     return Ot(),0;
65 }