#include <bits/stdc++.h>
#define pb push_back
#define fi first
#define se second
#define mp make_pair
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
int readint(){
int x=0,f=1; char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
const int N=5000500;
int n,a[N],val[N],pref[N];
vector<int> pos[N];
struct info{
ll mn_pref,mx_pref,mn_suff,mx_suff,tag;
}st[4*N];
int main(){
scanf("%d",&n);
for(int i=1;i<=n;i++) scanf("%d",&a[i]),pos[a[i]].pb(i);
//build(1,1,n);
for(int i=1;i<=n;i++) val[i]=1;
int ans=0;
for(int v=1;v<=n;v++){
if(pos[v].empty()) continue;
for(int j:pos[v]) val[j]=0;
// for(int j:pos[v]) modify(1,1,n,j,n,-1);
for(int i=1;i<=n;i++) pref[i]=pref[i-1]+val[i];
for(int l=1;l<=n;l++){
int cnt=0;
for(int r=l;r<=n;r++){
cnt+=(a[r]==v?1:0);
if(abs(pref[r]-pref[l-1])<=cnt) ans=max(ans,cnt);
}
}
// for(int j:pos[v]) modify(1,1,n,j,n,-1);
for(int j:pos[v]) val[j]=-1;
}
printf("%d\n",ans);
return 0;
}
Compilation message
sequence.cpp: In function 'int main()':
sequence.cpp:31:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
31 | scanf("%d",&n);
| ~~~~~^~~~~~~~~
sequence.cpp:32:29: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
32 | for(int i=1;i<=n;i++) scanf("%d",&a[i]),pos[a[i]].pb(i);
| ~~~~~^~~~~~~~~~~~
/usr/bin/ld: /tmp/cc8AGtZC.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccF4L28C.o:sequence.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/cc8AGtZC.o: in function `main':
grader.cpp:(.text.startup+0x2a4): undefined reference to `sequence(int, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status
