LeetCode #1180: Count Substrings with Only One Distinct
β’ 101 words β’ 1 min
LeetCode #1180: Count Substrings with Only One Distinct:
python
class Solution:
def countLetters(self, s: str) -> int:
def f(n):
# if n == 1:
# return 1
# if n == 2:
# return 3
# if n == 3:
# return 6
# if n == 4:
# return 10
return (n * (n + 1)) // 2
ans = 0
prev = None
q = 0
for c in s:
# aaa b
if c != prev:
ans += f(q)
prev = c
q = 1
else:
## prev = c
q += 1
ans += f(q)
return ans