Remove_Invalid_Parenthesis.py

backtracking/Remove_Invalid_Parenthesis.py

@@ -0,0 +1,50 @@
+def isParenthesis(c):
+	return ((c == '(') or (c == ')')) 
+
+def isValidString(str):
+	cnt = 0
+	for i in range(len(str)):
+		if (str[i] == '('):
+			cnt += 1
+		elif (str[i] == ')'):
+			cnt -= 1
+		if (cnt < 0):
+			return False
+	return (cnt == 0)
+	
+# method to remove invalid parenthesis 
+def removeInvalidParenthesis(str):
+	if (len(str) == 0):
+		return
+		
+	visit = set()
+	
+	q = []
+	temp = 0
+	level = 0
+	
+	q.append(str)
+	visit.add(str)
+	while(len(q)):
+		str = q[0]
+		q.pop(0)
+		if (isValidString(str)):
+			print(str)
+			
+			level = True
+		if (level):
+			continue
+		for i in range(len(str)):
+			if (not isParenthesis(str[i])):
+				continue
+				
+			temp = str[0:i] + str[i + 1:] 
+			if temp not in visit:
+				q.append(temp)
+				visit.add(temp)
+
+expression = "()())()"
+removeInvalidParenthesis(expression)
+expression = "()v)"
+removeInvalidParenthesis(expression)
+