CF817D Imbalanced Array
题目传送门
解题思路
AC代码
#include<cstdio>
#include<iostream>
using namespace std;
long long n,s,tail,a[1000005],f[1000005],minl[1000005],minr[1000005],maxl[1000005],maxr[1000005];
int main()
{
scanf("%lld",&n);
for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
f[1]=0;
tail=1;
for(int i=1;i<=n;i++)
if(a[i]>a[f[tail]])
{
minl[i]=i-1;
f[++tail]=i;
}
else
{
while(a[i]<a[f[tail]]&&tail>=1)tail--;
minl[i]=f[tail];
f[++tail]=i;
}
f[1]=n+1;
tail=1;
for(int i=n;i>=1;i--)
if(a[i]>a[f[tail]])
{
minr[i]=i+1;
f[++tail]=i;
}
else
{
while(a[i]<=a[f[tail]]&&tail>=1)tail--;
minr[i]=f[tail];
f[++tail]=i;
}
a[0]=a[n+1]=2147483647;
f[1]=0;
tail=1;
for(int i=1;i<=n;i++)
if(a[i]<a[f[tail]])
{
maxl[i]=i-1;
f[++tail]=i;
}
else
{
while(a[i]>a[f[tail]]&&tail>=1)tail--;
maxl[i]=f[tail];
f[++tail]=i;
}
f[1]=n+1;
tail=1;
for(int i=n;i>=1;i--)
if(a[i]<a[f[tail]])
{
maxr[i]=i+1;
f[++tail]=i;
}
else
{
while(a[i]>=a[f[tail]]&&tail>=1)tail--;
maxr[i]=f[tail];
f[++tail]=i;
}
for(int i=1;i<=n;i++)
s+=a[i]*1ll*(1ll*(i-maxl[i])*(maxr[i]-i)-1ll*(i-minl[i])*(minr[i]-i));
cout<<s;
}
谢谢