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Count number of equal pairs in a string
Basic Accuracy: 42.85% Submissions: 7 Points: 1

Given a string, find the number of pairs of characters that are same. Pairs (s[i], s[j]), (s[j], s[i]), (s[i], s[i]), (s[j], s[j]) should be considered different.

Example 1:

Input:
S = "air"
Output: 3
Explanation: 3 pairs that are equal:
(S[0], S[0]), (S[1], S[1]) and (S[2], S[2])

​Example 2:

Input: 
S = "aa"
Output: 4
Explanation: 4 pairs that are equal:
(S[0], S[0]), (S[0], S[1]), (S[1], S[0])
and (S[1], S[1])


Your Task:
You don't need to read input or print anything. Your task is to complete the function equalPairs() which takes the string S as input and returns the number of equal pairs as described in the problem description.


Expected Time Complexity: O(|S|).
Expected Auxiliary Space: O(1).


Constraints:
1<=|S|<=105

 

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Count number of equal pairs in a string

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