2019 牛客暑期多校训练营 第四场 C sequence 区间问题

#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int maxn = 3e6+5;
const ll inf = 1e18+5;
ll a[maxn];
int l[maxn],r[maxn];
ll sum[maxn];
struct NO{
	int l,r;
	ll mi,mx;
}no[maxn<<2];
void build(int p,int l,int r){
	no[p].l = l;
	no[p].r = r;
	if(l==r){
		no[p].mi = sum[l];
		no[p].mx = sum[l];
		return ;
	}
	int mid = (l+r)>>1;
	build(p*2,l,mid);
	build(p*2+1,mid+1,r);
	no[p].mi = min(no[p<<1].mi , no[p<<1|1].mi);
	no[p].mx = max(no[p<<1].mx , no[p<<1|1].mx);
}
ll getmin(int p,int l,int r){
	if(no[p].l>=l&&no[p].r<=r){
		return no[p].mi;
	}
	int mid = (no[p].l+no[p].r)>>1;
	ll ans = inf;
	if(l<=mid)ans = min(ans,getmin(p*2,l,r));
	if(r>mid)ans = min(ans,getmin(p*2+1,l,r));
	return ans;
}
ll getmax(int p,int l,int r){
	if(no[p].l>=l&&no[p].r<=r){
		return no[p].mx;
	}
	int mid = (no[p].l+no[p].r)>>1;
	ll ans = -inf;
	if(l<=mid)ans = max(ans,getmax(p*2,l,r));
	if(r>mid)ans = max(ans,getmax(p*2+1,l,r));
	return ans;
}

int main()
{	
#ifdef ACM_LOCAL
    freopen("./in.txt", "r", stdin);
    freopen("./out.txt", "w", stdout);
#endif
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%lld",&a[i]);
		l[i] = i;	r[i] = i;
	}
	sum[0] = 0; a[0] =a[n+1] = -1e6-6;
	for(int i=1;i<=n;i++){
		scanf("%lld",&sum[i]);
		sum[i] = sum[i-1]+sum[i];
	}
	build(1,1,n);
	for(int i=1;i<=n;i++){while(a[l[i]-1]>=a[i])l[i] = l[l[i] - 1];
	}
	for(int i=n;i>=1;i--){while(a[r[i]+1]>=a[i]) r[i] = r[r[i] + 1];
	}
	ll ans = -1e18+5;
	for(int i=1;i<=n;i++ ){
		if(a[i]>0){
			ll x1 = getmax(1,i,r[i]);
			ll x2 = getmin(1,l[i]-1,i-1);
			ans = max(ans,(x1-x2)*a[i]);	
		}else if(a[i]<0){
			ll x1 = getmin(1,i,r[i]);
			ll x2 = getmax(1,l[i]-1,i-1);
			ans = max(ans,(x1-x2)*a[i]);
		}else ans = max(ans,0ll);
	}
	printf("%lld\n",ans);
	return 0;
}