Implement lexGreaterPermutation function

[SjxSubham]

Intuition

Size of string is in [1,300]. Approach must be O(n^2) or O(n^2 logn).
When can a string be greater than another string of the same length?
if and only if for all characters at j in [0,i] s[j] = t[j]
and s[i+1]>t[i+1]
where i +1 < n (for proper indexing)

Approach

1. Create a frequency map of string s, initialise ans as empty string
2. Run a loop from i=0 to i =n-1
   a. Try to match the first ith characters of s and target (0 to i-1 in 0 indexing)
   b. for the ith (0 indexed) character of target, find the first character greater than it in the remaining frequency map
   c. if no such character found continue
   d. else for all indices from i +1 onwards till n-1, put all remaining chars of map in ascending order.
   e. if ans is empty string, set ans as found string, else set ans as minimum between ans and found string
3. return ans

[github-actions]

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