Given a string containing only two characters i.e. R and K (like RRKRRKKKKK). The task is to find the maximum value of N for a subsequence possible of the form R—N times and then K—N times (i.e. of the form R^N K^N).
Note: String of k should be started after the string of R i.e. first k that would be considered for ‘K’ string must occur after the last R of the ‘R’ string in the given string. Also, the length of the resulting subsequence will be 2*N.
If we take R’s at indexes 0, 1, 2, 4, 5 and K’s at indexes 6, 7, 10, 11, 12
then we get a maximum subsequence of the form R^N K^N, where N = 5.
If we take R at index 4( or 5 or 6 or 7) and K at index 8
then we get the desired subsequence with N = 1.
- Calculate the number of R’s before a K .
- Calculate the number of K’s after a K, including that K.
- Store them in a table with a number of R’s in table[x] and a number of K’s in table[x].
- Minimum of the two gives the value of n for each K and we will the return the maximum n.
Below is the implementation of the above approach:
Time Complexity: O(n) where ln is the length of the substring.
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