Encrypt the string - 2
Easy Accuracy: 31.64% Submissions: 851 Points: 2

You are given a string S. Every sub-string of identical letters is replaced by a single instance of that letter followed by the hexadecimal representation of the number of occurrences of that letter. Then, the string thus obtained is further encrypted by reversing it [ See the sample for more clarity ]. Print the Encrypted String.

Note: All Hexadecimal letters should be converted to Lowercase letters.

Example 1:

Input:
S = "aaaaaaaaaaa"
Output:
ba
Explanation:
aaaaaaaaaaa
Step1: a11 (a occurs 11 times)
Step2: a11 is ab [since 11 is b in
Step3: ba [After reversing]

Example 2:

Input:
S = "abc"
Output:
1c1b1a
Explanation:
abc
Step1: a1b1c1
Step2: 1c1b1a [After reversing]

You don't need to read input or print anything. Your task is to complete the function encryptString() which takes a String S and returns the answer.

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

Constraints
1 <= |S| <= 105

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