Add solution #77

Author: JoshCrozier

README.md

@@ -53,6 +53,7 @@
 67|[Add Binary](./0067-add-binary.js)|Easy|
 73|[Set Matrix Zeroes](./0073-set-matrix-zeroes.js)|Medium|
 74|[Search a 2D Matrix](./0074-search-a-2d-matrix.js)|Medium|
+77|[Combinations](./0077-combinations.js)|Medium|
 83|[Remove Duplicates from Sorted List](./0083-remove-duplicates-from-sorted-list.js)|Easy|
 88|[Merge Sorted Array](./0088-merge-sorted-array.js)|Easy|
 94|[Binary Tree Inorder Traversal](./0094-binary-tree-inorder-traversal.js)|Easy|

solutions/0077-combinations.js

@@ -0,0 +1,31 @@
+/**
+ * 77. Combinations
+ * https://leetcode.com/problems/combinations/
+ * Difficulty: Medium
+ *
+ * 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.
+ */
+
+/**
+ * @param {number} n
+ * @param {number} k
+ * @return {number[][]}
+ */
+var combine = function(n, k) {
+  const result = [];
+  backtrack(result, n, k);
+  return result;
+};
+
+function backtrack(result, n, k, combination = [], offset = 1) {
+  if (combination.length === k) {
+    result.push(combination);
+  } else {
+    while (offset <= n) {
+      backtrack(result, n, k, [...combination, offset], ++offset);
+    }
+  }
+}