BZOJ 1636: [Usaco2007 Jan]Balanced Lineup

#include<cstdio>
#include<cstring>
#include<algorithm>
#define g getchar()
#define ll long long
#define inf 0x3f3f3f3f
using namespace std;
inline ll read(){
ll x=0,f=1;char ch=g;
for(;ch<'0'||ch>'9';ch=g)if(ch=='-')f=-1;
for(;ch>='0'&&ch<='9';ch=g)x=x*10+ch-'0';
return x*f;
}
inline void out(ll x){
int a[25],wei=0;
if(x<0)putchar('-'),x=-x;
for(;x;x/=10)a[++wei]=x%10;
if(wei==0){puts("0");return;}
for(int j=wei;j>=1;--j)putchar('0'+a[j]);
putchar('\n');
}
int n,b[50005],a[50005],c[50005],Q;
int init1(){
for(int i=1;i<=n;++i){
b[i]=a[i];
for(int j=1;j<i&-i;j<<=1)
b[i]=max(b[i],b[i-j]);
}
}
int query1(int l,int r){
int ans=a[r];
for(;;){
ans=max(ans,a[r]);
if(r==l)break;
for(r-=1;r-l>=r&-r;r-=r&-r)
ans=max(ans,b[r]);
}
return ans;
}
int init2(){
for(int i=1;i<=n;++i){
c[i]=a[i];
for(int j=1;j<i&-i;j<<=1)
c[i]=min(c[i],c[i-j]);
}
}
int query2(int l,int r){
int ans=a[r];
for(;;){
ans=min(a[r],ans);
if(l==r)break;
for(r-=1;r-l>=r&-r;r-=r&-r)
ans=min(ans,c[r]);
}
return ans;
}
int main(){
//  freopen("","r",stdin);
//  freopen("","w",stdout);
n=read();Q=read();
for(int i=1;i<=n;++i)a[i]=read();
init1();
init2();
for(;Q--;){
int l=read(),r=read();
out(query1(l,r)-query2(l,r));
}
return 0;
}