def longestPalindrome(s):
# 建立DP array size is len（arr）*len（arr）
dp = [[False]*len(s) for i in range(len(s))]
# 初始化 start end 指针
StartIndex = 0
EndIndex = 0
# dp算法填充表格,start 为行 end为列 要右上部分
for i in range(len(s)):
start = i
end = i
while start>=0:
#对角线上的都是T
if start==end:
dp[start][end] = True
#如果相邻，就不用了看中间的了
elif start+1==end:
dp[start][end] = s[start]==s[end]
#不相邻，看看首先是不是相等，相等然后向中间看是否相等
else:
dp[start][end] = s[start]==s[end] and dp[start+1][end-1]
if dp[start][end] and (end-start+1)>(EndIndex-StartIndex+1):
StartIndex = start
EndIndex = end
start-=1
return s[StartIndex:EndIndex+1]
a = 'akbka'
print(longestPalindrome(a))
