Leetcode 7. 整数反转(模拟)

题目链接在这里：7. 整数反转 - 力扣（LeetCode）

这道题学习了list类型不能在没有定义长度的情况下直接访问里面的第i个元素，应该使用append或者在开始的时候就a = [0 for _ in range(n)]

 1 class solution:
 2     def longest(self,s : str)->str:
 3         ans = 0
 4         lft = rgt = 0
 5         n = len(s)
 6         f=[[False] * n for _ in range(n)]
 7         ans = 1
 8         for i in range(n):
 9             f[i][i] = True
10         for i in range(n-1):
11             if s[i] == s[i+1] :
12                 f[i][i+1] = True
13                 ans = 2
14                 lft = i
15             else:
16                 f[i][i+1] = False
17         for length in range(3, n+1):
18             for i in range(n-length+1):
19                 j = i+length - 1 
20                 # print(i,j)
21                 if s[i] == s[j]:
22                     f[i][j]=f[i+1][j-1]
23                 if f[i][j]==True:
24                     ans = length
25                     lft = i
26         return s[lft: lft+ans]
27 
28 if __name__=="__main__":
29     s = "ccc"
30     an = solution.longest(self=0,s=s)
31     print(an)