Added python solution to 22.GenerateParenthesis (#121)

Author: JoyKrishan

Algorithms/Medium/22_GenerateParentheses/Solution.py

@@ -0,0 +1,22 @@
+class Solution:
+    def generateParenthesis(self, n: int) -> List[str]:
+        stack = []
+        res = []
+        
+        def parenthesis_backtrack(open_paren, close_paren):
+            if open_paren == close_paren == n:
+                res.append("".join(stack))
+                return 
+            
+            if open_paren < n:
+                stack.append("(")
+                parenthesis_backtrack(open_paren + 1, close_paren)
+                stack.pop()
+            
+            if open_paren > close_paren:
+                stack.append(")")
+                parenthesis_backtrack(open_paren, close_paren + 1)
+                stack.pop()
+                
+        parenthesis_backtrack(0, 0)
+        return res