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Author: PrashantVIT1

Data Structures/Stacks/Check redundant brackets.py

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+"""Check redundant brackets
+For a given expression in the form of a string, find if there exist any redundant brackets or not. It is given that the expression contains only rounded brackets or parenthesis and the input expression will always be balanced.
+A pair of the bracket is said to be redundant when a sub-expression is surrounded by unnecessary or needless brackets.
+Example:
+Expression: (a+b)+c
+Since there are no needless brackets, hence, the output must be 'false'.
+Expression: ((a+b))
+The expression can be reduced to (a+b). Hence the expression has redundant brackets and the output will be 'true'.
+Input Format :
+The first and the only line of input contains a string expression, without any spaces in between.
+Output Format :
+The first and the only line of output will print either 'true' or 'false'(without the quotes) denoting whether the input expression contains redundant brackets or not.
+Constraints:
+0 <= N <= 10^6
+Where N is the length of the expression.
+Time Limit: 1 second
+Sample Input 1:
+a+(b)+c
+Sample Output 1:
+true
+Explanation:
+The expression can be reduced to a+b+c. Hence, the brackets are redundant.
+Sample Input 2:
+(a+b)
+Sample Output 2:
+false"""
+
+def checkRedundantBrackets(expression) :
+  s=expression
+  le = len(s)
+  l=[]
+  for i in range(le):
+    if s[i]=="(":  # checks open bracket
+      l.append("(") # put open brackets to stack
+    elif s[i] in "+-*/": #check char in the string
+      l.append(s[i])      #if it an operator then put it into the stack
+    elif s[i] ==")":       # checks close bracket
+      if l[-1]=="(":       # and if there is no operator in the stack
+          return True      # then its redundant and further code will not run
+      elif l[-1] in "+-*/":        # if it has operator 
+        
+        while l[-1]!="(":          # then pop till we don't get open bracket
+          l.pop()                  
+        l.pop()                     #pop open bracket
+  return False                      #it is false if no redundant bracket is found till end
+
+expression=input("Enter the expression:\n")
+print("output:")
+if checkRedundantBrackets(expression):
+  print('true')
+else:
+  print('false')
+"""
+Time complexity: O(n)
+Space complexity: O(n)
+"""