loj2051 「HNOI2016」序列

ref

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
typedef long long ll;
int n, q, a[100005], l[100005], r[100005], sta[100005], din, blc, bel[100005], st[100005][19], mii[17], mlg[100005];
ll sl[100005], sr[100005], now, ans[100005];
struct Ques{
	int ll, rr, id;
}qu[100005];
bool cmp(Ques x, Ques y){
	if(bel[x.ll]!=bel[y.ll])	return bel[x.ll]<bel[y.ll];
	if(bel[x.ll]&1)	return x.rr<y.rr;
	return x.rr>y.rr;
}
int getPos(int x, int y){
	int l=mlg[y-x+1], k=y+1-mii[l];
	return a[st[x][l]]<a[st[k][l]]?st[x][l]:st[k][l];
}
ll calL(int x, int y){
	int p=getPos(x, y);
	return (ll)a[p]*(y-p+1)+sr[x]-sr[p];
}
ll calR(int x, int y){
	int p=getPos(x, y);
	return (ll)a[p]*(p-x+1)+sl[y]-sl[p];
}
int main(){//freopen("sequence9.in", "r", stdin);
	cin>>n>>q;
	blc = sqrt(n);
	for(int i=1; i<=n; i++){
		scanf("%d", &a[i]);
		bel[i] = (i - 1) / blc + 1;
		st[i][0] = i;
	}
	for(int i=1; i<=q; i++){
		scanf("%d %d", &qu[i].ll, &qu[i].rr);
		qu[i].id = i;
	}
	sort(qu+1, qu+1+q, cmp);
	for(int i=1; i<=n; i++){
		while(din && a[sta[din]]>=a[i])	din--;
		if(din)	l[i] = sta[din];
		sta[++din] = i;
	}
	din = 0;
	for(int i=n; i; i--){
		r[i] = n + 1;
		while(din && a[sta[din]]>=a[i])	din--;
		if(din)	r[i] = sta[din];
		sta[++din] = i;
	}
	mii[0] = 1;
	for(int i=1; i<=16; i++)
		mii[i] = mii[i-1] << 1;
	for(int i=2; i<=n; i++)
		mlg[i] = mlg[i>>1] + 1;
	for(int j=1; j<=16; j++)
		for(int i=1; i<=n; i++){
			st[i][j] = st[i][j-1];
			int k=i+mii[j-1];
			if(k<=n)	st[i][j] = (a[st[i][j-1]]<a[st[k][j-1]])?st[i][j-1]:st[k][j-1];
		}
	for(int i=1; i<=n; i++)
		sl[i] = sl[l[i]] + (ll)(i - l[i]) * a[i];
	for(int i=n; i; i--)
		sr[i] = sr[r[i]] + (ll)(r[i] - i) * a[i];
	int gtl=qu[1].ll, zzh=gtl-1;
	for(int i=1; i<=q; i++){
		while(gtl>qu[i].ll)	now += calL(--gtl, zzh);
		while(zzh<qu[i].rr)	now += calR(gtl, ++zzh);
		while(gtl<qu[i].ll)	now -= calL(gtl++, zzh);
		while(zzh>qu[i].rr)	now -= calR(gtl, zzh--);
		ans[qu[i].id] = now;
	}
	for(int i=1; i<=q; i++)
		printf("%lld\n", ans[i]);
	return 0;
}