[LeetCode Sync] Runtime - 135 ms (63.29%), Memory - 59.7 MB (26.74%)

Author: NinePiece2

Solutions/0077-combinations/README.md

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+<p>Given two integers <code>n</code> and <code>k</code>, return <em>all possible combinations of</em> <code>k</code> <em>numbers chosen from the range</em> <code>[1, n]</code>.</p>
+
+<p>You may return the answer in <strong>any order</strong>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 4, k = 2
+<strong>Output:</strong> [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]
+<strong>Explanation:</strong> There are 4 choose 2 = 6 total combinations.
+Note that combinations are unordered, i.e., [1,2] and [2,1] are considered to be the same combination.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 1, k = 1
+<strong>Output:</strong> [[1]]
+<strong>Explanation:</strong> There is 1 choose 1 = 1 total combination.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= n &lt;= 20</code></li>
+	<li><code>1 &lt;= k &lt;= n</code></li>
+</ul>

Solutions/0077-combinations/solution.py

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+class Solution:
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        result = []
+        temp = []
+
+        def dfs(i: int):
+            if len(temp) == k:
+                result.append(temp[:])
+                return
+            if i > n:
+                return
+            temp.append(i)
+            dfs(i + 1)
+            temp.pop()
+            dfs(i + 1)
+        
+        dfs(1)
+        return result