Check if concatenation of two strings is balanced or not in Python

Suppose we have two bracket sequences s and t with only these characters '(' and ')'. We have to check whether the concatenated string of s and t is balanced or not. The concatenation can be done by s | t or t | s.

So, if the input is like s = "()()))", t = "()(()(", then the output will be True because if we concatenate t | s, then we will get "()(()(()()))", which is balanced.

To solve this, we will follow these steps −

• Define a function is_balanced_parenthesis() . This will take string
• stack := a new list
• for i in range 0 to size of string, do
  • if string[i] is same as '(', then
    • push string[i] into stack
  • otherwise,
    • if stack is empty, then
      • return False
    • otherwise,
      • pop from stack
• if stack is not empty, then
  • return False
• return True
• From the main method do the following −
• if is_balanced_parenthesis(s + t) is true, then
  • return True
• return is_balanced_parenthesis(t + s)

Let us see the following implementation to get better understanding −

Example

 Live Demo

def is_balanced_parenthesis(string):
   stack = []
   for i in range(len(string)):
      if string[i] == '(':
         stack.append(string[i])
      else:
         if len(stack) == 0:
            return False
         else:
            stack.pop()
   if len(stack) > 0:
      return False
   return True
def solve(s, t):
   if is_balanced_parenthesis(s + t):
      return True
   return is_balanced_parenthesis(t + s)
s = "()()))"
t = "()(()("
print(solve(s, t))

Input

"()()))", "()(()("

Output

True

Arnab Chakraborty

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Updated on: 30-Dec-2020

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