Given a string s
consisting only of characters a, b and c.
Return the number of substrings containing at least one occurrence of all these characters a, b and c.
Example 1:
Input: s = "abcabc"
Output: 10
Explanation: The substrings containing at least one occurrence of the characters
a, b and c are "abc", "abca", "abcab", "abcabc", "bca", "bcab", "bcabc", "cab",
"cabc" and "abc" (again).
Example 2:
Input: s = "aaacb"
Output: 3
Explanation: The substrings containing at least one occurrence of the characters
a, b and c are "aaacb", "aacb" and "acb".
Example 3:
Input: s = "abc"
Output: 1
Constraints:
3 <= s.length <= 5 x 10^{4}
s
only consists of a, b or c characters.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

class Solution:
def numberOfSubstrings(self, s: str) > int:
res = i = 0
count = {c: 0 for c in 'abc'}
for j in range(len(s)):
count[s[j]] += 1
while all(count.values()):
count[s[i]] = 1
i += 1
res += i
return res
'''
`last` will record the position of last occurrence.
If the ending index of substring is `i`,
the starting position should be on the left of min(last),
in order to have all 3 different letters.
And in this case, the starting index can be in range [0, min(last)],
min(last) + 1 in total.
'''
class Solution:
def numberOfSubstrings(self, s: str) > int:
res, last = 0, [1] * 3
for i, c in enumerate(s):
last[ord(c)  97] = i
res += 1 + min(last)
return res
