Simple Python Solution

Use two pointer to find a consecutive substring with the same char, sum them up and add it to result, then start looking to the left and to the right.

```
def countSubstrings(self, s):
"""
:type s: str
:rtype: int
"""
ret = 0
left, right = 0, 0
while left < len(s):
while right < len(s) and s[right] == s[left]:
right += 1
ret += self.sum(right - left)
l, r = left-1, right
while l >= 0 and r < len(s) and s[r] == s[l]:
ret += 1
l -= 1
r += 1
left = right
return ret
def sum(self, n):
s = 0
for i in range(1, n + 1):
s += i
return s
```