题解 | 最长回文子串

s = input().strip()
n = len(s)

max_len = 1

dp = []
for i in range(n):
    in_list = []
    for j in range(n):
        in_list.append(False)
    dp.append(in_list)

for i in range(n):
    dp[i][i] = True

for i in range(n-1):
    if s[i] == s[i+1]:
        dp[i][i+1] = True
        max_len = 2

for length in range(3,n+1):
    for i in range(n-length+1):
        j = i + length - 1
        if s[i] == s[j] and dp[i+1][j-1]:
            dp[i][j] = True
            if length > max_len:
                max_len = length

print(max_len)