39 lines
840 B
C++
39 lines
840 B
C++
#include <iostream>
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#include <cstring>
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#include <cstdio>
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using namespace std;
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int s[1005];
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int dp[1005][1005];
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int max(int a,int b)
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{
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return a>b?a:b;
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}
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int main()
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{
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int n;
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while (cin>>n&&n)
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{
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memset(dp,0,sizeof(dp));
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for (int i=1;i<=n;i++)
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cin>>s[i];
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for (int l=1;l<=n;l++)
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{
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for (int i=1;i+l-1<=n;i++)
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{
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int j=i+l-1;
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int p=2;
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if (i==j)
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p=1;
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if (s[j]==s[i])
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dp[i][j]=p+dp[i+1][j-1];
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else
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dp[i][j]=max(dp[i][j-1],dp[i+1][j]);
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}
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}
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int ans=0;
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for (int i=0;i<=n;i++)
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ans=max(ans,dp[1][i]+dp[i+1][n]);
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cout<<ans<<endl;
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}
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}
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