Question

We are given a string S of length N consisting only of letters ' A ' and/or 'B'. Our goal is to obtain a string in the format "A...AB...B" (all letters 'A' occur before all letters 'B') by deleting some letters from S. In particular, strings consisting only of letters ' A ' or only of letters ' B ' fit this format. Write a function: def solution(S) that, given a string S, returns the minimum number of letters that need to be deleted from S in order to obtain a string in the above format. Examples: 1. Given S= "BAAABAB", the function should return 2. We can obtain "AAABB" by deleting the first occurrence of 'B' and the last occurrence of 'A'. 2. Given S= "BBABAA", the function should return 3. We can delete all occurrences of 'A' or all occurrences of ' B '. 3. Given S = "AABBBB", the function should return 0. We do not hava th dolate anu lattore hanarica tha riven ctrinn is alrapdy in tha

Answer 1

Below is the Python code for the solution function:

Python

def solution(S):

# Initialize the variables

count_a = 0

count_b = 0

deletions = 0

# Iterate through the string

for ch in S:

# Count the occurrences of 'A' and 'B'

if ch == 'A':

count_a += 1

else:

count_b += 1

# Check if the current character is 'B' and all previous characters are 'A'

if ch == 'B' and count_a > 0:

deletions += 1

# Check if there are any 'A's after any 'B's

if count_b > 0 and count_a > 0:

deletions += 1

return deletions

So, the above function is one that efficiently tells the minimum number of deletions required to obtain a string in the specified format. It iterates through the string, keeping track of the occurrences of 'A' and 'B'.

Therefore, It checks for instances where 'B' appears before 'A' and increments the deletion count accordingly. Then, it handles the case where both 'A's and 'B's exist and ensures the string adheres to the desired format.