Add solution #216

Author: JoshCrozier

README.md

@@ -151,6 +151,7 @@
 213|[House Robber II](./0213-house-robber-ii.js)|Medium|
 214|[Shortest Palindrome](./0214-shortest-palindrome.js)|Hard|
 215|[Kth Largest Element in an Array](./0215-kth-largest-element-in-an-array.js)|Medium|
+216|[Combination Sum III](./0216-combination-sum-iii.js)|Medium|
 217|[Contains Duplicate](./0217-contains-duplicate.js)|Easy|
 219|[Contains Duplicate II](./0219-contains-duplicate-ii.js)|Easy|
 225|[Implement Stack using Queues](./0225-implement-stack-using-queues.js)|Easy|

solutions/0216-combination-sum-iii.js

@@ -0,0 +1,37 @@
+/**
+ * 216. Combination Sum III
+ * https://leetcode.com/problems/combination-sum-iii/
+ * Difficulty: Medium
+ *
+ * Find all valid combinations of k numbers that sum up to n such that the following
+ * conditions are true:
+ * - Only numbers 1 through 9 are used.
+ * - Each number is used at most once.
+ *
+ * Return a list of all possible valid combinations. The list must not contain the same
+ * combination twice, and the combinations may be returned in any order.
+ */
+
+/**
+ * @param {number} k
+ * @param {number} n
+ * @return {number[][]}
+ */
+var combinationSum3 = function(k, n) {
+  const result = [];
+
+  function backtrack(history, sum, start) {
+    if (sum > n) return;
+    if (history.length === k && sum === n) {
+      result.push(history);
+      return;
+    }
+    for (let i = start; i < 10; i++) {
+      backtrack([...history, i], sum + i, i + 1);
+    }
+  }
+
+  backtrack([], 0, 1);
+
+  return result;
+};