Completed

Problem 1.py

@@ -0,0 +1,16 @@
+class Solution:
+    def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
+        res = []
+        def helper(i, sub, cursum):
+            nonlocal res
+            if cursum > target or i >= len(candidates):
+                return
+            if cursum==target:
+                res.append(sub.copy())
+
+            for c in range(i, len(candidates)):
+                sub.append(candidates[c])
+                helper(c, sub, cursum+candidates[c])
+                sub.pop()
+        helper(0, [], 0)
+        return res

Problem 2.py

@@ -0,0 +1,24 @@
+class Solution:
+    def addOperators(self, num: str, target: int) -> List[str]:
+        n = len(num)
+        res = []
+        def dfs(i,sofar, value, prev): #123
+            if i >= n and value == target:
+                # print(sofar, value)
+                res.append("".join(sofar))
+                return
+
+            for j in range(i, n):
+                if not sofar:
+                    dfs(j+1, [num[i:j+1]], int(num[i:j+1]), int(num[i:j+1]))
+                else:   
+                    dfs(j+1, sofar + ['+'] + [num[i:j+1]], value+int(num[i:j+1]), int(num[i:j+1]) )
+                    dfs(j+1, sofar + ['-'] + [num[i:j+1]], value-int(num[i:j+1]), -int(num[i:j+1]) )
+
+                    #for *, bc of bodmas, need to have prev value so that we will add or minus ( opps of last operation), multiply it with current one and then add it back to value(which is prev res or res sofar)
+                    dfs(j+1, sofar + ['*'] + [num[i:j+1]], value-prev + prev*int(num[i:j+1]),  prev*int(num[i:j+1]))
+
+                if num[i]=='0': #so that it doesn't consider vals like 00, 05, 005 etc. hence after 1 0, don't dfs more
+                    break
+        dfs(0, [], 0, None)
+        return res