Iinit

Author: kumailn

Python/Generate_Paranthesis.py

@@ -0,0 +1,20 @@
+#Question: Generate all possible pairs of parenthesis for a given number n
+#Solution: Recursive backtracking, keep count of left brackets and right brackets
+#Difficulty: Medium 
+
+def generateParenthesis(n):
+        """
+        :type n: int
+        :rtype: List[str]
+        """
+        results = []
+        def helper(results, string, leftCount, rightCount):
+            #If we've reached the base case where no more brackets can be added, append the current string to our array
+            if not leftCount and not rightCount: results += [string]
+            #If there are still left brackers to be added, add left bracket and recall function with 1 less left bracket but 1 more right bracket (Since we've opened a new bracket that needs to be closed)
+            if leftCount: helper(results, string + "(", leftCount-1, rightCount+1)
+            #If there are right brackets that need to be added, add 1 then recall function with 1 less right bracket
+            if rightCount: helper(results, string + ")", leftCount, rightCount-1)
+        #Call initially with empty array, empty string, n left brackets and no right brackets
+        helper(results, "", n, 0)
+        return results