Description
You are given a string s
and a character c
. Return the total number of substrings of s
that start and end with c
.
Β
Example 1:
Input: s = "abada", c = "a"
Output: 6
Explanation: Substrings starting and ending with "a"
are: "abada"
, "abada"
, "abada"
, "abada"
, "abada"
, "abada"
.
Example 2:
Input: s = "zzz", c = "z"
Output: 6
Explanation: There are a total of 6
substrings in s
and all start and end with "z"
.
Β
Constraints:
1 <= s.length <= 105
s
andc
consistΒ only of lowercase English letters.
Solution
Python3
class Solution:
def countSubstrings(self, s: str, c: str) -> int:
N = len(s)
count = res = 0
for x in s:
if x == c:
count += 1
res += count
return res