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Python – Extract range of Consecutive Similar elements ranges from string list

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  • Last Updated : 20 Aug, 2022
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Given a list, extract range of consecutive similar elements.

Input : test_list = [2, 3, 3, 3, 8, 8] 
Output : [(2, 0, 0), (3, 1, 3), (8, 4, 5)] 
Explanation : 2 occurs from 0th to 0th index, 3 from 1st to 3rd index.

Input : test_list = [3, 3, 3] 
Output : [(3, 0, 3)] 
Explanation : 3 from 0th to 3rd index. 

Approach: Using loop

This is a brute way to tackle this problem. In this, we loop for each element and get a similar element range. These are traced and appended in list accordingly with elements.

Python3




# Python3 code to demonstrate working of
# Consecutive Similar elements ranges
# Using loop
 
# initializing list
test_list = [2, 3, 3, 3, 8, 8, 6, 7, 7]
 
# printing original list
print("The original list is : " + str(test_list))
 
res = []
idx = 0
while idx < (len(test_list)):
    strt_pos = idx
    val = test_list[idx]
     
    # getting last pos.
    while (idx < len(test_list) and test_list[idx] == val):
        idx += 1
    end_pos = idx - 1
     
    # appending in format [ele, strt_pos, end_pos]
    res.append((val, strt_pos, end_pos))
 
# printing result
print("Elements with range : " + str(res))


Output:

The original list is : [2, 3, 3, 3, 8, 8, 6, 7, 7] Elements with range : [(2, 0, 0), (3, 1, 3), (8, 4, 5), (6, 6, 6), (7, 7, 8)]

Time Complexity: O(n2)

Space Complexity: O(n)

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