HackerRank 'Alternating Characters' Solution

Martin Kysel · February 27, 2015

Short Problem Definition:

Shashank likes strings in which consecutive characters are different. For example, he likes ABABA, while he doesn’t like ABAA. Given a string containing characters A and B only, he wants to change it into a string he likes. To do this, he is allowed to delete the characters in the string.

Your task is to find the minimum number of required deletions.



time complexity is O(N\*T)

space complexity is O(1)


If two following characters are the same, you have to delete one of them. A sequence of x equal characters will require (x-1) deletions.


if __name__ == '__main__':
    t = input()
    for _ in range(t):
    	s = raw_input()
    	delete_cnt = 0
    	for i in range(1,len(s)):
            if s[i] == s[i-1]:
            	delete_cnt +=1
        print delete_cnt

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