// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
- insert(x),erase(x)
- find_by_order(k): return iterator to the k-th smallest element
- order_of_key(x): the number of elements that are strictly smaller
*/
#include<bits/stdc++.h>
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
uniform_real_distribution<> pp(0.0,1.0);
#define int long long
#define ld long double
#define pii pair<int,int>
#define piii pair<int,pii>
#define mpp make_pair
#define fi first
#define se second
const int inf=1e18;
const int mod=998244353;
const int maxn=3005;
const int bl=650;
const int maxs=655;
const int maxm=200005;
const int maxq=1000005;
const int maxl=25;
const int maxa=1000000;
const int root=3;
int power(int a,int n){
int res=1;
while(n){
if(n&1) res=res*a%mod;
a=a*a%mod;n>>=1;
}
return res;
}
const int iroot=power(3,mod-2);
const int base=131;
int n,a[maxn],cnt[maxn][maxn];
int C,c[maxn],S[maxn];
int cal(){
int res=0;
for(int i=n;i>=1;i--){
for(int l=1;l<=n-i+1;l++){
int r=l+i-1;
cnt[l][r]=(a[l]==a[r])*(2+cnt[l-1][r+1]);
}
}
{//contain midpoint
for(int i=1;i<=n;i++){
int l=i;
for(int j=1;j<=C;j++) c[j]=0;
set<int> s;
s.insert(a[l]);
c[a[l]]++;
while(l>1 && a[l-1]>=a[l]){
l--;
s.insert(a[l]);
c[a[l]]++;
}
for(int j=1;j<=C;j++) S[j]=S[j-1]+c[j];
int Min=-1,cc=0;
for(int j=i+1;j<=n;j++){
if(a[i]>a[j]){
if(Min!=-1){
if(a[j]==Min) cc++;
else break;
}
else{
Min=a[j],cc=1;
}
}
else{
if(!c[a[j]]) s.insert(a[j]);
c[a[j]]--;
if(!c[a[j]]) s.erase(a[j]);
}
int last=C;
if(!s.empty()) last=*s.begin();
else res=max(res,j-l+1+cnt[l-1][j+1]);
res=max(res,S[last-1]*2+(S[last]-S[last-1]+min(0LL,-c[last]))*2+cc);
}
}
}
{//not contain midpoint
auto query = [&](int l,int r){
while(l>=1 && r<=n && a[l]==a[r]) l--,r++;
res=max(res,r-l-1);
if(l<1 || r>n) return;
int lt=l;
for(int j=1;j<=C;j++) c[j]=0;
set<int> s;
s.insert(a[lt]);
c[a[lt]]++;
while(lt>1 && a[lt-1]>=a[lt]){
lt--;
s.insert(a[lt]);
c[a[lt]]++;
}
for(int j=1;j<=C;j++) S[j]=S[j-1]+c[j];
for(int j=r;j<=n;j++){
if(a[l]>a[j]) break;
if(!c[a[j]]) s.insert(a[j]);
c[a[j]]--;
if(!c[a[j]]) s.erase(a[j]);
int last=C;
if(!s.empty()) last=*s.begin();
else res=max(res,j-lt+1+cnt[lt-1][j+1]);
res=max(res,S[last-1]*2+(S[last]-S[last-1]+min(0LL,-c[last]))*2+r-l-1);
}
};
for(int i=1;i<n;i++){
if(i>1) query(i-1,i+1);
query(i,i+1);
}
}
return res;
}
void solve(){
cin >> n >> C;
for(int i=1;i<=n;i++) cin >> a[i];
int ans=cal();
for(int i=1;i<=n;i++) a[i]=C-a[i]+1;
reverse(a+1,a+n+1);
ans=max(ans,cal());
cout << ans << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
int test=1;//cin >> test;
while(test--) solve();
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2396 KB |
Output is correct |
| 2 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 3 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 4 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 5 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 6 |
Incorrect |
1 ms |
2396 KB |
Output isn't correct |
| 7 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2396 KB |
Output is correct |
| 2 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 3 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 4 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 5 |
Correct |
1 ms |
2396 KB |
Output is correct |
| 6 |
Incorrect |
1 ms |
2396 KB |
Output isn't correct |
| 7 |
Halted |
0 ms |
0 KB |
- |
