hdu 4745 Two Rabbits

思路：求最长回文子串的长度！
代码如下：

 

 1 #include<iostream>

 2 #include<stdio.h>

 3 #include<algorithm>

 4 #include<iomanip>

 5 #include<cmath>

 6 #include<cstring>

 7 using namespace std;

 8 int s[3001],dp[3001][3001];

 9 int dfs(int p,int q)

10 {

11       if(dp[p][q]!=-1) return dp[p][q];

12       if(p>q) return dp[p][q]=0;

13       dp[p][q]=max(dfs(p+1,q),dfs(p,q-1));

14       if(s[p]==s[q]) dp[p][q]=max(dp[p][q],dfs(p+1,q-1)+1);

15       return dp[p][q];

16 }

17 int main()

18 {

19     int n;

20     while(scanf("%d",&n)&&n){

21             for(int i=1;i<=n;i++){

22                   scanf("%d",&s[i]);

23                   s[2*n+i]=s[n+i]=s[i];

24             }

25             int ans=0;

26             memset(dp,-1,sizeof(dp));

27             for(int i=1;i<=n;i++)

28                   ans=max(ans,dfs(i,2*n+i-1));

29             printf("%d\n",ans);

30     }

31     return 0;

32 }

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