BZOJ4491: 我也不知道题目名字是什么

#include<cstdio>
#include<cctype>
#include<queue>
#include<cstring>
#include<algorithm>
#define rep(i,s,t) for(int i=s;i<=t;i++)
#define dwn(i,s,t) for(int i=s;i>=t;i--)
#define ren for(int i=first[x];i;i=next[i])
using namespace std;
const int BufferSize=1<<16;
char buffer[BufferSize],*head,*tail;
inline char Getchar() {
	if(head==tail) {
		int l=fread(buffer,1,BufferSize,stdin);
		tail=(head=buffer)+l;
	}
	return *head++;
}
inline int read() {
    int x=0,f=1;char c=Getchar();
    for(;!isdigit(c);c=Getchar()) if(c==‘-‘) f=-1;
    for(;isdigit(c);c=Getchar()) x=x*10+c-‘0‘;
    return x*f;
}
const int maxn=50010;
const int maxnode=6000010;
struct Query {int l,r,id,next;}Q[maxnode];
int n,cnt,ans[maxn],f[maxn],g[maxn],A[maxn],first[maxn*4],res[maxn*4];
void AddQuery(int o,int ql,int qr,int id) {
	Q[++cnt]=(Query){ql,qr,id,first[o]};first[o]=cnt;
}
void solve(int o,int l,int r) {
	int mid=l+r>>1,lc=o<<1,rc=lc|1;
	if(l==r) {
		for(int i=first[o];i;i=Q[i].next) ans[Q[i].id]=max(ans[Q[i].id],1);
		res[o]=1;
	}
	else {
		for(int i=first[o];i;i=Q[i].next) {
			Query& T=Q[i];
			if(T.r<=mid) AddQuery(lc,T.l,T.r,T.id);
			else if(T.l>mid) AddQuery(rc,T.l,T.r,T.id);
			else if(T.l!=l||T.r!=r) AddQuery(lc,T.l,mid,T.id),AddQuery(rc,mid+1,T.r,T.id);
		}
		solve(lc,l,mid);solve(rc,mid+1,r);
		res[o]=max(res[lc],res[rc]);
		int ok;
		ok=1;f[mid+1]=1;
		rep(i,mid+2,r) {
			if(A[i-1]<A[i]) ok=0;
			f[i]=f[i-1]+ok;
		}
		ok=1;if(A[mid]<A[mid+1]) ok=0;f[mid]=ok;
		dwn(i,mid-1,l) {
			if(A[i+1]>A[i]) ok=0;
			f[i]=f[i+1]+ok;
		}
		res[o]=max(res[o],f[l]+f[r]);
		ok=1;g[mid+1]=1;
		rep(i,mid+2,r) {
			if(A[i-1]>A[i]) ok=0;
			g[i]=g[i-1]+ok;
		}
		ok=1;if(A[mid]>A[mid+1]) ok=0;g[mid]=ok;
		dwn(i,mid-1,l) {
			if(A[i+1]<A[i]) ok=0;
			g[i]=g[i+1]+ok;
		}
		res[o]=max(res[o],g[l]+g[r]);
		for(int i=first[o];i;i=Q[i].next) {
			Query& T=Q[i];
			if(T.l<=mid&&T.r>mid) ans[T.id]=max(ans[T.id],max(f[T.l]+f[T.r],g[T.l]+g[T.r]));
			if(T.l==l&&T.r==r) ans[T.id]=max(ans[T.id],res[o]);
		}
	}
}
int main() {
	n=read();rep(i,1,n) A[i]=read();
	int m=read();
	rep(i,1,m) {
		int l=read(),r=read();
		AddQuery(1,l,r,i);
	}
	solve(1,1,n);
	rep(i,1,m) printf("%d\n",ans[i]);
	return 0;
}