Given a string S, the task is to find the largest lexicographical string with no more than K consecutive occurrence of an element by either re-arranging or deleting the elements.

Examples:

Input: S = “baccc” 
K = 2 
Output: Result = “ccbca” 
Explanation: Since K=2, a maximum of 2 same characters can be placed consecutively. 
No. of ‘c’ = 3. 
No. of ‘b’ = 1. 
No. of ‘a’ = 1. 
Since the largest lexicographical string has to be printed, therefore, the answer is “ccbca”.
Input: S = “xxxxzaz” 
K = 3 
Output: result = “zzxxxax” 

Approach:

1. Form a frequency array of size 26, where index i is chosen using (character in string – ‘a’).
2. Initialize an empty string to store corresponding changes.
3. for i=25 to 0, do:

• If frequency at index i is greater than k, then append (i + ‘a’) K-times. Decrease frequency by K at index i.find the next greatest priority element and append to answer and decrease frequency at respective index by 1.
• If frequency at index i is greater than 0 but less than k, then append (i + ‘a’) times it’s frequency.
• If frequency at index i is 0, then that index cannot be used to form an element and therefore check for next possible highest priority element.

#algorithms #arrays #greedy #hash #strings #lexicographic-ordering