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Solutions.py

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+## Problem1 Combination Sum (https://leetcode.com/problems/combination-sum/)
+## Time Complexity : O(n * 2^(m+n))
+## Space Complexity : O(n^2)
+
+class Solution(object):
+    def combinationSum(self, candidates, target):
+        """
+        :type candidates: List[int]
+        :type target: int
+        :rtype: List[List[int]]
+        """
+        ## backtracking approach:
+        ## - I cab either choose or not choose 
+        ## - If choosing adding it to the sum and recurssing
+        ## - not choosing and recurssing again. 
+
+        output = []
+        def helper(idx,sm,path):
+            ## boundary  conditions - if out of  bounds
+            if sm > target or idx >= len(candidates):
+                return 
+            ## base condition  -- if sum reached the target
+            if sm == target:
+                output.append(path[:])
+                return
+
+            path.append(candidates[idx])
+            helper(idx,sm+candidates[idx],path)
+            path.pop()
+            helper(idx+1,sm,path)
+
+        helper(0,0,[])
+        return output
+
+
+
+
+
+## Problem2 Expression Add Operators(https://leetcode.com/problems/expression-add-operators/)
+## Time Complexity :
+## Space Complexity : 
+