Finding the minimum number of required deletions to have a non-repeating string

I wrote code for the following problem:

Given a string, print out the number of deletions required so that the adjacent alphabets are distinct.

Please suggest different methods by which I can increase the speed of execution.

tst = int(input())
for i in range(0,tst):
str = input()
length = len(str)
str = list(str)
j=0;
count = 0
while(j<length):
if(j+1<length):
if((str[j] == str[j+1])):
del str[j+1]
count+=1
length-=1
else:
j+=1
else:
j+=1
print(count)


del str[j+1]


When you remove one character from a string, all subsequent characters need to be shifted into the hole that you create. That changes your algorithm from O(Length) to a worst-case scenario of O(Length2), if every character is the same.

Additionally, your inner loop looks a lot like C code. Here is one way to reformulate it.

def count_consecutive_deletions(s):
deletions = 0
for i in range(1, len(s)):
if s[i] == s[i - 1]:
deletions += 1
return deletions

def testcases():
for _ in range(int(input())):
yield input()

for case in testcases():
print(count_consecutive_deletions(case))