Python – Matching Pairs of Brackets

Sometimes, while working with Python data, we can have a problem in which we need to pair all the elements with the suitable closing brackets, and can have data associated with pairing. This kind of problem is classic application of Stack Data Structure and can have usage across many domains. Let’s discuss a certain way in which this task can be done.

Input : test_list = [(‘(‘, 1), (‘(‘, 2), (‘)’, 3), (‘)’, 4)]
Output : [(2, 3), (1, 4)]

Input : test_list = [(‘(‘, 1), (‘)’, 4)]
Output : [(1, 4)]

Method : Using stack DS + loop
The combination above functionalities can be used to solve this problem. In this, we make a new pair with each opening bracket and when the corresponding closing bracket comes using LIFO technique, we form a pair with that closing bracket.

# Python3 code to demonstrate working of
# Matching Pairs of Brackets
# Using stack DS + loop

# initializing list
test_list = [('(', 7), ('(', 9), (')', 10), (')', 11), ('(', 15), (')', 100)]

# printing original list
print("The original list is : " + str(test_list))

# Matching Pairs of Brackets
# Using stack DS + loop
stck = []
res = []
for ele1, ele2 in test_list:
    if '(' in ele1:
        stck.append((ele1, ele2))
    elif ')' in ele1:
        res.append((stck.pop()[1], ele2))

# printing result
print("The paired elements : " + str(res))

Output :

The original list is : [('(', 7), ('(', 9), (')', 10), (')', 11), ('(', 15), (')', 100)]
The paired elements : [(9, 10), (7, 11), (15, 100)]

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