ZOJ 2527(最长等差数列)

随便给一串数列,求最长等差数列

3方水过,回头附n^2logn算法 (dp[i][j][k]=dp[i][k]+1)

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<cctype>
#include<iostream>
#include<functional>
#include<algorithm>
using namespace std;
#define MAXN (10000+10)
int n,a[MAXN];
int main()
{
    while (scanf("%d",&n)!=EOF)
    {
        for (int i=1;i<=n;i++) scanf("%d",&a[i]);
        sort(a+1,a+1+n);
        int ans=2;
        for (int i=1;i<=n;i++)
            for (int j=i+1;j<=n;j++)
            {
                int dd=a[j]-a[i],now=j,tot=2;
                for (int k=j+1;k<=n;k++)
                {
                    if (a[k]-a[now]==dd) 
                    {
                        tot++;
                        now=k;
                    }
                }   
                ans=max(ans,tot);

            }       
        cout<<ans<<endl;

    }

    return 0;
}