Palindromic Substrings
Given a string, your task is to count how many palindromic substrings in this string. The substrings with different start indexes or end indexes are counted as different substrings even they consist of same characters.
Example
Example1
Input: "abc"
Output: 3
Explanation:
3 palindromic strings: "a", "b", "c".
Example2
Input: "aba"
Output: 4
Explanation:
4 palindromic strings: "a", "b", "a", "aba".
Notice
The input string length won't exceed 1000
分析
以中间2位向两边扩展,注意判断left, right 是在范围内
class Solution:
"""
@param str: s string
@return: return an integer, denote the number of the palindromic substrings
"""
def countPalindromicSubstrings(self, str):
# write your code here
n = len(str)
def expand(i,j):
cnt = 0
while 0 <= i and j < n:
if str[i] != str[j]:
break
i -= 1
j += 1
cnt += 1
return cnt
res = 0
for i in range(n):
res += expand(i,i)
res += expand(i,i+1)
return res
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