leetcode 5. 最长回文子串 dp

public class Solution
{
	public String longestPalindrome(String s)
	{
		int len=s.length();
		if(len==1)return s;
		boolean dp[][]=new boolean[len][len];
		for(int i=0;i<len;++i)dp[i][i]=true;
		
		int maxlen=1;
		int begin=0;
		
		for(int L=2;L<=len;++L)
		{
			for(int i=0;i<len;++i)
			{
				int j=i+L-1;
				if(j>=len)break;
				if(s.charAt(i)==s.charAt(j))
				{
					if(L<=3)dp[i][j]=true;
					else dp[i][j]=dp[i+1][j-1];
				}
				else dp[i][j]=false;
				
				if(dp[i][j]==true)
				{
					if(j-i+1>maxlen)
					{
						maxlen=j-i+1;
						begin=i;
					}
				}
			}
		}
		
		return s.substring(begin, begin+maxlen);
	}
}