Problem Description:
code show as below:
#include<bits/stdc++.h>
using namespace std;
const int N=105;
int n;
int a[N];
int l[N],r[N];
void dp1()
{
int f[N];
int len=1;
f[1]=a[1];
l[1]=1;
for(int i=2;i<=n;i++){
if(f[len]<a[i]) f[++len]=a[i];
else{
int pos=lower_bound(f+1,f+1+len,a[i])-f;
f[pos]=a[i];
}
l[i]=len;
}
}
void dp2()
{
int f[N];
int len=1;
f[1]=a[n];
r[n]=1;
for(int i=n-1;i>=1;i--){
if(f[len]<a[i]) f[++len]=a[i];
else{
int pos=lower_bound(f+1,f+1+len,a[i])-f;
f[pos]=a[i];
}
r[i]=len;
}
}
int main()
{
cin>>n;
for(int i=1;i<=n;i++) cin>>a[i];
dp1();
dp2();
int ans=0;
for(int i=1;i<=n;i++){
ans=max(ans,l[i]+r[i]-1);
}
cout<<n-ans;
return 0;
}
to sum up:
Calculate the longest ascending subsequence from left to right and from right to left respectively, and then traverse all cases to obtain the optimal solution