36 lines
569 B
C++
36 lines
569 B
C++
#include<cstdio>
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#include<algorithm>
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using namespace std;
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const int oo=1e9;
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const int maxn=10005;
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int n;
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int a[maxn],dp[maxn],f1[maxn],f2[maxn];
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void DP(int *f)
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{
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fill(dp,dp+maxn,oo);
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for(int i=0;i<n;i++)
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{
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int k=lower_bound(dp+1,dp+n+1,a[i])-dp;
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dp[k]=a[i];
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f[i]=k;
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}
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}
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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while(scanf("%d",&n)==1)
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{
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for(int i=0;i<n;i++) scanf("%d",&a[i]);
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DP(f1);
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reverse(a,a+n);
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DP(f2);
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int res=0;
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for(int i=0;i<n;i++)
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res=max(res,min(f1[i],f2[n-i-1])*2-1);
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printf("%d\n",res);
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}
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return 0;
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}
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