My idea is moving the symmetric line from the left to the right.

```
class Solution(object):
def countBinarySubstrings(self, s):
length = len(s)
ans = 0
for index in range(length-1):
if s[index] != s[index+1]:
ans += 1
step = 1
left_index = index - step
right_index = index +step+1
while left_index >=0 and right_index < len(s):
if s[left_index]==s[index] and s[index+1]==s[right_index]:
ans += 1
else:
break
step += 1
left_index = index - step
right_index = index + step + 1
return ans
```