Combinations

Author: Shikha-code36

Backtracking/77-Combinations.py

@@ -0,0 +1,38 @@
+'''Leetcode- https://leetcode.com/problems/combinations/'''
+'''
+Given two integers n and k, return all possible combinations of k numbers out of the range [1, n].
+
+You may return the answer in any order.
+
+Example 1:
+
+Input: n = 4, k = 2
+Output:
+[
+  [2,4],
+  [3,4],
+  [2,3],
+  [1,2],
+  [1,3],
+  [1,4],
+]
+'''
+def combine(n, k):
+    result = []
+
+    def backtrack(start,comb):
+        if len(comb) == k:
+            result.append(comb.copy())
+            return
+
+        for i in range(start,n+1):
+            comb.append(i)
+            backtrack(i+1,comb)
+            comb.pop()
+
+    backtrack(1,[])
+    return result
+
+#T: O(k.n^k)
+#T: O(k. n!/(n-k)!k!)
+#S: O(n)

README.md

@@ -12,4 +12,5 @@ Check the notes for the explaination - [Notes](https://stingy-shallot-4ea.notion
     - [x] [Subsets-II](Backtracking/78-Subsets.py)
     - [x] [Permutations](Backtracking/46-Permutations.py)
     - [x] [Permutations II](Backtracking/47-Permutations-II.py)
+    - [x] [Combinations](Backtracking/77-Combinations.py)