1
class Solution(object):
2
    def countPalindromicSubsequence(self, s):
3
        d = defaultdict(list)
4
        for i, c in enumerate(s):
5
            d[c].append(i)
6
        ans = 0
7
        for el in d:
8
            if len(d[el]) < 2:
9
                continue
10
            a = d[el][0]
11
            b = d[el][-1]
12
            ans += len(set(s[a + 1 : b]))
13
        return ans