题解 | #最长回文子串#

• 中心拓展法来求解，O(n^2)

string = input()

# 中心拓展法
def expand(s, i, j):
    ans = 0
    while i >=0 and j < len(s) and s[i] == s[j]:
        ans = j - i + 1
        i = i - 1
        j = j + 1
    return ans

ans = 0
for i in range(len(string)):
    ans = max(ans, expand(string, i, i))
    ans = max(ans, expand(string, i, i+1))
print(ans