Examples :
Input: {[] {()}} Output: Balanced Input : [{} {} (] Output: Unbalanced Approach # 1: Using the stack
One one approach for checking balanced parentheses is to use a stack.Every time open parentheses are encountered, push them onto the stack, and when closed parentheses are encountered, match them to the top of the stack and insert them. If the end of the stack is empty, return Balanced, otherwise, Unbalanced .
| # Python3 code to check
# balanced parentheses in expression open_list = [ " [" , " {" , "(" ] close_list = [ "]" , "}" , ")" ]
# Function for checking parentheses def check (myStr): stack = [] for i in myStr: if i in open_list: stack.append (i) elif i in close_list: pos = close_list.index (i) if (( len (stack)" 0 ) and (open_list [pos] = = stack [ len (stack) - 1 ])): stack.pop () else : return "Unbalanced" if len (stack) = = 0 : return "Balanced"
# Driver code string = "{[] {()}}" print (string, "-" , check (string)) string = "[{} {}) (]" print (string, "-" , check (string)) |
Output:
{[] {()}} - Balanced [{} {}) (] - Unbalanced Approach # 2 Using the queue
First match open parentheses with matching closing parentheses. Iterate over the specified expression using "i" if "i" — open brackets, add to queue if "i" — closing brackets, check if the queue is empty or "i" — top of the queue, if yes, return "Unbalanced", otherwise "Balanced".
| # Python3 code to check
# balanced parentheses in expression def check (expression): open_tup = tuple ( ’ ({[’ ) close_tup = tuple ( ’)}]’ ) map = dict ( zip (open_tup, close_tup)) queue = [] for i in expression: if i in open_tup: queue.append ( map [i]) elif i in close_tup: if not queue or i! = queue.pop (): return "Unbalanced" return "Balanced"
# Driver code string = "{[] {()}}" print (string, "-" , check (string)) |
Exit od:
{[] {()}} - Balanced Approach # 3: on based on liquidation
On each iterations, the innermost parentheses are removed (replaced with an empty string). If we get an empty string, our initial one will be balanced; otherwise not.
| # Python3 code to check
# balanced brackets in expression def check (my_string): brackets = [ ’()’ , ’{}’ , ’[]’ ] while any (x in my_string for x in brackets): for br in brackets: my_string = my_string.replace (br,’ ’) return not my_string
# Driver code string = "{[] {()}}" print (string, "-" , " Balanced " if check (string) else "Unbalanced" ) |
Exit:
{[] {()}} - Balanced
